Teacher Resource Pack Guide Science 7 - For CSS Secondary Standard SCIENCE For Class 7 1 Division of Syllabus into three terms Teacher’s Guide Fully Solved Exercises Model Papers Teacher Resource Pack Guide Science 7 Table of Contents Sr. No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Description Division of Syllabus (Complete) Unit # 1: Human organ Systems Unit # 2: Transport in humans and plants Unit # 3: Reproduction in plants Unit # 4: Environment and feeding relationship Unit # 5: Water Unit # 6: Structure of an atom Unit # 7: Physical and chemical changes and process Unit # 8: Transmission of heat Unit # 9: Dispersion of light Unit # 10: Sound waves Unit # 11: Circuit and electric current Unit # 12: Transport in humans and plants Page No. Division of Syllabus Total Unit – 4 Available weeks – 10 st Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Available weeks – 14 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 2 1 Term Unit # 1 Human organ Systems Unit # 1 Human organ Systems Unit # 1 (Exercise + Revision) + Unit # 2 Transport in humans and plants Unit # 2 Transport in humans and plants Unit # 2 (Exercise + Revision) + Unit # 3 Reproduction in plants Unit # 3 Reproduction in plants Unit # 3 (Exercise + Revision) + Unit # 4 Environment and feeding relationship Unit # 4 Environment and feeding relationship Review Exercise + Revision Unit#4 + Revision Unit#1 Revision unit 2, 3, 4 Total Unit– 6 nd 2 Term Unit # 5 Water Unit # 6 Structure of an Atom Unit # 7 Physical and chemical changes andprocesses Unit # 8 Transmission of heat Unit # 9 Dispersion of light Unit # 10 Sound waves Revision Unit 5, 6, 7 Teacher Resource Pack Guide Science 7 Week 14 Total Chapter – 2 Revision of Unit 8, 9, 10 Available weeks – 8 3rd Term Week 1 Week 2 Week 3 Week 4 Unit # 11 Unit # 12 Week 5 Revision of 1st term Week 6 Revision of 2nd term Week 7 Revision of 3rd term Week 8 Complete revision ‘Detailed Division of Syllabus’ 1st term Week 1 Day 1 Day 2 Unit– 1 T – 1.1: T – 1.1: T – 1.2: T – 1.3: T – 1.4: T – 1.5: Human Organ system Human digestive system Human digestive system Digestion and its importance + Digestion of various kinds of foods Disorder of digestive system + Factors and preventive measures Revision Test Exercise – 1 T – 1.6: T – 1.6.1: T – 1.6.2: T – 1.7: T – 1.8: Day 4 Day 5 Day 6 Human respiratory system + Breathing Respiration in humans and its mechanism + Breathing and burning process Disorders of respiratory system + T – 1.8.1, T – 1.8.2 T – 1.8.3, T – 1.8.4 Revision + Test exercise – 2 Review exercise Week 3 Day 1 Review exercise Day 2 Revision of Complete Chapter Day 3 Day 4 Day 5 Day 6 Week 2 Day 1 Day 2 Day 3 Day 3 Day 4 Day 5 3 Unit – 2: T – 2.1: T – 2.2: Transport in humans and plants Transport system in human + Circulatory system and its components(1st half) T – 2.2: Circulatory system and its components (2nd half) T – 2.3: Working of circulatory system Teacher Resource Pack Guide Day 6 Week 4 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Science 7 T – 2.3: T – 2.5: T – 2.6: T – 2.7: T – 2.7: Week 5 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Unit – 3: T – 3.1: T – 3.2: T – 3.3: Week 6 Day 1 Day 2 T – 3.4: T – 3.4: Day 3 T – 3.5: T – 3.6: Day 4 Day 5 Day 6 Week 7 Day 1 Day 2 Day 3 Day 4 T – 4.4: Day 5 Day 6 4 Unit – 4: T – 4.1: T – 4.1.1: T – 4.2: T – 4.3: T – 4.3: Scientific development for dysfunctional body parts Revision Test exercise – 1 Disorders in circulatory system due to diet Transport system in plants Movement of food, water and gases in plants (1st half) Movement of food, water and gases in plants (1st half) Revision + Test exercise – 2 Review exercise Review exercise Revision of Complete Chapter Reproduction in plants Pollination Factors involved in cross pollination + Cross pollinated plants Revision + Test exercise – 1 Sexual and asexual reproduction (1st half: asexual reproduction) Sexual and asexual reproduction (2nd half: sexual reproduction) Fertilization Seed and fruit formation Revision Test exercise – 2 Review exercise Environment and feeding relationship Ecosystem Components of ecosystem Habitat Kinds of habitat (1st half) Kinds of habitat (2nd half) Features of animals for particular habitat (1st half) T – 4.5: Adaptations of living things to daily and yearly changes in their habit (2nd half) T – 4.6: Adaptations in animals and plants Teacher Resource Pack Guide Science 7 particular habitat Week 8 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 T – 4.7: T – 4.8: T – 4.9: T – 4.9: T – 4.10: Revision + Test exercise – 1 Respond to daily environment Food chain + Relationship between producers and consumers (1st half) Relationship between producers and consumers (2nd half) Food web Revision + Test exercise – 2 Week 9 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Review exercise Review exercise Revision of complete Chapter – 4 Revision unit – 1 Revision unit – 1 Revision unit – 1 Week 10 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Revision unit – 2 Revision unit – 2 Revision unit – 3 Revision unit – 3 Revision unit – 4 Revision unit – 4 1st Term Unit # 1 Week 1 & 2 HUMAN ORGAN SYSTEM Lesson 1 + 2 Topic: (Human digestive system) Teaching objectives: ⦁ Explain that human body works by the coordination of different organ system. ⦁ Explain the components and functions of digestive ⦁ Explain the route of food in human digestive system. system. Key vocabulary: Organ systems, digestive system, integumentary system, lymphatic system, skeletal system, alimentary canal, pharynx, oesophagus, pepsin. Materials required: ⦁ Board (White/Black), Marker/Chalk, CSS – Science for class – 7, Model/Charts, of organs of digestive system. , Worksheets (for each student), frog, dissecting box, chloroform. Summary of the chapter: As students are going to start 1st chapter, tell them about the chapter first: Introduce the chapter by linking it with cellular hierarchy. i.e. 5 Teacher Resource Pack Guide Science 7 Cell tissues organs organ systems organism Tell them we are now going to start organ systems which form when different organs perform specific function incoordination to accomplish different tasks. This chapter will cover the digestive system and respiratory system. Both systems provide raw materials for energy production e.g. digestive system provides minerals, carbohydrate, proteins and fats and respiratory system provides oxygen for respiration. There are different organ systems in human body. Introduction: Introduce the topic. Tell students they are going to investigate digestive system and its components. Ask some questions to refresh their knowledge e.g. a) What happen to food we take in? b) Which organs take part in digestion? c) What would happen if digestive system fails to perform its duty? Transfer students responses on board. (Correct one) Arrange the pictures of organs of digestive system. Explanation and Development: Activity: Take the class to biology lab. Dissect the frog. Reveal its digestive system. First describe the general overview of components of the digestive system. Then explain it with the help of model/chart. Explanation: First comes the oral cavity. Explain the functions of tongue, teeth and saliva. Also explain that it is the first stage of digestion. Physical and chemical digestion begin here. Discuss the breakdown of carbohydrate. Then comes the pharynx, explain it the way as did above. The next destination of food is oesophagus. Explain the working of it by the following diagram. You may enter a solid particle in oesophagus of frog and push it downward to show its movement and role of peristalsis. Then came the stomach the next junction of food. Expose the stomach of frog and explain the functions and structure of stomach. Also describe the role of hydrochloric acid in stomach and the compounds that are digested here. (Here ends the first lesson. Show and introduce other organs of digestive system from dissected frog, so that it may easily be understandable for tomorrow lessons.) In next lesson, first revise the previous lesson by asking different questions. ask students, if they have any query. Solve, it if any then start the next lesson in the some way as done the Lesson – 1. If charts and models may not be available, draw these organs on board and label it. Summary:After explanation of whole lesson, revise all the main points from board. Ask students to select one of the organs of their choice and draw its diagram on their note books. Ask them to label it and describe its role in digestion. Check the students effort and appreciate them. Inform students about tomorrow’s topic. Lesson 3 Topic: (Digestion and its importance) T.1.2 – T.1.3 Digestion of carious kinds of foods 6 Teacher Resource Pack Guide Science 7 Teaching objectives: ⦁ Explain that without digestion energy cannot be obtained. ⦁ Explain that purpose of digestion is to obtain nutrients from food. ⦁ Explain the digestive process. Key vocabulary: Assimilation, nutrients, salivary amylase, pepsin, pancreatic juice. Materials required: ⦁ Board (White/Black), Chalk/Marker, CSS – Science – 7, Model showing the digestion process. Introduction / A bag of flavoured popcorns warm up Activity 1. Pop a bag of popcorn and set it in the classroom. 2. Ask: “What do you smell? See? From what you smell and see, what is now happening inside your mouth?” (The mouth is producing more saliva (fluids produced in your mouth to help digestion). 3. Ask: Does what you smell make you hungry? Does what you see make you want to eat this bag of popcorn? (Use the answers to get the students to discuss how sight and smell affect their desire to eat. Tell the students that the sight and smell of food actually DOES START the digestive process. Your body is ready for the food even before you’ve taken even one bite of food.) 4. Pass the popcorn bag around to the students and let them take a few pieces. Ask them to take ONE piece and place it in their mouth, letting it stay there UNCHEWED for a minute or two. Then have them begin to chew the popcorn SLOWLY, paying attention to the amount of saliva in their mouth, AND to how the TASTE and TEXTURE of the food changes by the contact with the saliva and then due to the process of chewing. Explain the role and importance of saliva in digestion. Tell them saliva helps in physical as well as chemical break down of food with the help of salivary gland it contains in today’s lesson, we will understand the process of digestion. Exploration/Explanation Ask: “Why does our body performs digestion process?” (If students do not understand right away, ask further questions: “Why do we eat? What happens if we do not eat?”) Reinforce: “We need energy to be alive, to play, to learn, to read, and even to sit. Our Digestive System takes the food. We eat it and turn it into energy. Digestive system does this by breaking it down. This is called DIGESTION.” Steps in the Digestive Process: Simulate how our body digests food. NOTE: You may do this after lunch – ask the lunch room attendants if you can have one complete meal after lunch to use for the experiment (or you may bring in your own food – a sandwich or piece of fruit or cracker.) You’ll need the following items: Spray bottle (labeled as “SALIVA”) with water Bowl (labeled as “MOUTH”) • Tube (preferably clear, labeled “OESOPHAGUS”) Blender (labeled as “STOMACH”) Bottle (labeled as “GASTRIC ACIDS”) with water Two Forks and food smasher. Ask the Students to create a four column chart on their note books. To record what is happening to the food as the digestive process occurs step by step. The teacher will draw the chart on board as follows: Mouth Esophagus Stomach Intestines At each step, ask students write down where the food; what it looks like, and explain what the body is doing at each point along the digestive tract (four columns.) For example, Step 1: “Where is the food?” (In the bowl labeled as Mouth.) “What does it look like?” (A cracker.) 7 Teacher Resource Pack Guide Science 7 “What is the body doing?” (The mouth is making saliva, the esophagus is moving, and stomach is making juices.) Make observations and record information throughout the entire lesson. Step # 1: Sight and Smell: Provide students the background knowledge as follows. The first part of the digestion process happens even BEFORE we eat our food. When we see or smell food, our mouth creates a watery juice. “Does anyone know what that juice is called?” (Saliva). Ask a volunteer student to add 1 or 2 sprays of “saliva” into the ‘mouth’ bowl.) “What is the tube called that connects our throat with our stomach?” (The esophagus.) “The esophagus begins to move.” (Show how the esophagus starts to move – wave like motion to move the food down.) “Then the stomach starts to make special juices that help turn the food into fuel.” (Ask a volunteer) to pour stomach juices into the stomach (blender). Step # 2: In the Mouth: Digestion: Ask students to put the food from the tray in to the “mouth” (bowl). Ask: “How does your mouth break up the food?” (With the help of teeth, tongue.) “What do your teeth do?” (Chop, grind, smash, etc.) “What would happen if you put a piece of food in your mouth?” 1. Give a volunteer two forks to break down the food. 2. Ask: “What happened to the food?” (It was broken up into chunks.) 3. Ask: “How did the food get smaller?” (The teeth chopped up the food.) 4. Ask: “Besides chopping the food, what else does the mouth do? What kind of juice is our mouth making the whole time we are eating?” Remember – saliva contains enzymes that help break down the food. 5. “Let’s see what saliva does to the food.” Demonstrate by spraying “saliva” into the “mouth” bowl. Continue to mash and chop. 6. Ask: “What happened when the saliva started working on the food?” (The food got softer and became more of a liquid.) Conclusion: “The mouth, with the saliva, the teeth and the tongue, mash the food up into small, soft parts so we can swallow it.” 7. “Observe: what does the food look like?” Ask students to record their observations. 8. Reinforce: “TEETH CHOP and GRIND the food when we take a bite. The TONGUE, which is a MUSCLE, moves food around in the mouth, and the watery juice that our mouth has been making, SALIVA, goes to work breaking down the food.” 9. Ask: “How does food pass through the throat to the stomach?” (We swallow the food at the back of our mouth and it travels down the esophagus into the stomach.) “The esophagus is a very STRONG tube. It has muscles in it that move food down to our stomach. It only takes about 10 seconds for food to get to the stomach.” 10. Make sure the food is broken down enough to go down the tube (oesophagus.) Do not actually put food in it because it may plug up and then is impossible to clean. Ask: “What happens if you don’t take the time to thoroughly break up the food in your mouth?” (The pieces may be too big to go down the esophagus and you could CHOKE.) (NOTE: you may not want to take the time to completely break up all of the food. Just tell the students to pretend and put it in the “stomach.”) Step # 3: In the Stomach: Digestion Now let’s see what happens in the stomach. Help students to predict by asking: What do you (students) think the stomach does? How does the stomach turn food into liquid?” (Ans: The stomach has muscles that continue to chew the food, and it also has digestive juices that help breakdown the food even further.) 8 Teacher Resource Pack Guide Science 7 Explain: “Now we are going to see what happens to the food in the stomach. To demonstrate, add more “gastric acids” to the mix so that the blender will have about 3-4 cups of “digested” food when you are finished. Run the blender on “Medium” or “High” to liquefy the food and turn it into a soupy paste. Pour the mix into a strong, clear zip lock bag, and have the students look at it, explaining that this is the digested food in the stomach (the bag.) Ask: “How long do you think it takes the stomach to digest food?” (It takes the stomach two-four hours to digest food.) “Foods like bread, cookies, and vegetables that contain carbohydrates, get digested first. Foods like meat that contain proteins, and the fat in food (like mayonnaise or butter) take longer time to digest.” Again, ask students record their observations. Ask them: What does the food look like in the stomach? What does the stomach do? etc. Extend: “Besides breaking down food through grinding and fluids, the digestive System also has two other important functions: ABSORBING NUTRIENTS from the food and then ELIMINATING what it doesn’t use.” Step # 4. The Small Intestine: Absorption: Do not put food in the tube because it is very difficult to clean! Ask: “Where does this paste go?” (Into the small intestine.) Ask: “What does the small intestine do with the food?” (The small intestine takes the nutrients from the food and puts them into the body. This is called ABSORPTION and this another important function of digestion. Ask: “How long is the small intestine?” (About 20 feet long in an adult.) Use charts and models to clarity the concepts. Step # 5. The Large Intestine: Elimination: Ask: “Where does the remaining digested food go after it leaves the small intestine?” Answer: To the large intestine. Conclusion and Assessment: To summarize and conclude the instruction, draw the Digestive System on the board. Use a series of “Ask and Respond” questions to assess the understanding of students. Home work: Assign the following questions as home work. Describe the importance of digestion. Describe the digestion of various kinds foods that happens during digestion. Lesson 4 Topic: (1.4: Disorders of digestive system) (1.5: Factors and preventive measures of constipation and diarrhea) Teaching objectives: ⦁ Explain that digestive system may suffer from some disorders. ⦁ Explain the diseases such as: diarrhea, constipation. ⦁ Explain the causes and preventive measures of diarrhea and constipation. Key vocabulary: Diarrhea, constipation, heart burn, ulcer, low fiber diet, anxiety. Materials required: ⦁ Board (White/Black), Marker/Chalk, CSS – Science for Class – 7. Teaching points: Working of digestive system may be disturbed due to improper diet. Diarrhea, constipation, heart burn and ulcer are some common diseases of digestive system. Diarrhea: Diarrhea is the increase in frequency of bowl movement. The stool becomes loose. Causes: It happens due to some bacteria, parasites and even viruses in taken by unhygienic food, very high fiber diet, anxiety, as a side effect of medication, etc. Due to all these reasons, the absorption of fluid by intestine decreases. As a result, stool becomes loose. Diarrhea can be diagnosed by its symptoms i.e. abdominal pain, cramping and in severe cases vomiting. 9 Teacher Resource Pack Guide Science 7 Constipation: Constipation is the inverse of diarrhea. In this condition, frequency of bowl movement decreases. The stool becomes hard and is difficult to pass because extra water is absorbed by intestines. Causes: Constipation is caused by poor diet rich in animal fat and low in fiber. This kind of diet increase the water absorption from intestines. Heart burn: Heart burn is the sensation of burning in lower chest along with a sour taste in throat and mouth. It usually occur after eating a big meal or while lying down. It can last for few minutes to few hours. Causes: When you eat, food passes from your mouth down a tube (about 10 inches long in most people) called the esophagus. To enter the stomach, the food must pass through an opening between the esophagus and stomach. This opening acts like a gate to allow food to pass into the stomach. Usually, this opening closes as soon as food passes through. But if it doesn't close, acid from your stomach can get through the opening and into your esophagus. This is called reflux. Stomach acid can irritate the esophagus and cause heartburn. Ulcer: Ulcers are sores on the lining of digestive tract. Digestive tract consists of esophagus, stomach, duodenum (the first part of the intestines) and intestines. Most ulcers are located in the duodenum. These ulcers are called duodenal ulcers. Ulcers located in the stomach are called gastric ulcers. Ulcers in the esophagus are called esophageal ulcers. Causes: A type of bacteria called Helicobacter pylori (H. pylori) causes many types of ulcers. Acid and other juices made by the stomach can contribute to ulcers by burning the lining of digestive tract. This can happen if the body makes too much acid or if the lining of digestive tract is damaged in some way. Physical or emotional stress may not necessarily cause an ulcer, but it can aggravate an ulcer if you have one as it produce more acid in stomach. Possible signs of an ulcer: Feel worse when you eat or drink. Stomach pain that wakes one up at night Heavy feeling, bloating, burning or dull pain in stomach Vomiting Unexpected weight loss Introduction: As students have previous knowledge of human digestive system. Ask them some questions that may lead them towards the today’s topic e.g. 1. What would happen if the epiglottis would not close after pushing food into esophagus? 2. Why do we feel sour taste in mouth after having big meal? 3. What would happen if large intestine could not absorb water from digested food? 4. What symptoms appear when they have high frequency of bowl movement? After having answers from students, introduce the today’s topic. Ask them they are going to explore answers of these questions as they are going to study disorders of digestive system. Development/Activity: Now, write the 1st disorder i.e. diarrhea on board. Assess student’s previous knowledge by asking some question e.g. 1. What do you know about diarrhea? 2. What does the doctor advice when you have diarrhea? After having answers, explain it thoroughly. Tell them the causative agents, symptoms, and preventive measures. Then, ask students to write how they would diagnose if some is suffering from diarrhea. In the same way, describe all the diseases of digestive system one by one. Activity: Arrange a presentation by school doctor. The aim of this presentation should be to inform students about digestive system diseases. Assessment: Distribute an activity sheet that students will complete during class or at home. In this activity sheet, students will pretend as doctor and will give their prognosis as a doctor. They will be given various scenario and they have to best identify the disorders based upon the provided information. 10 Teacher Resource Pack Guide Science 7 A discussion will be hold in which students will present what they believe affecting each patient then the teacher will decide and guide toward, relevant information. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ You are provided with the symptoms of some patients. Identify the disease and suggest the proper treatment. Be careful and diagnose wisely. 1. A young lad from Boy Scout troop spent the weekend in forest. He travelled few miles. During his journey, his eating routine badly disturbed. He could not have proper food and he had to face scarcity of water. Now he is facing difficulty to excrete. He is also having cramps and sour taste. Ans.__________________________________________________________________________ _____________________________________________________________________________ 2. A young girl has come to you. She has lost his body fluids due to vomiting and loose bowel. Ans.__________________________________________________________________________ _____________________________________________________________________________ Test Exercise – 1 A. 1. Choose the correct answer and fill the circle. Mr. Ali went to the hospital for the check-up of his body organ systems. Help him to know how many organ systems are there in body. eight nine ten eleven 2. Dr. Ahmed wants to do a check-up of oral cavity of a patient. Which part he will be mainly observing? mouth oesophagus stomach intestines 3. Which of the following is the actual site for the digestion of proteins? mouth stomach small intestine large intestine 4. The common name for colon is: liver small intestine large intestine gall bladder 5. The biomolecule broken down with the help of bile is: water protein fat carbohydrate B. Answer the following questions briefly. 1. Define epiglottis. Ans: Epiglottis is a flap of tissues on pharynx that act as a door to direct the food into esophagus and air into larynx. 2. Enlist the functions of small intestine. Ans: Small intestine performs the following functions: 1. Breaking down of food by using digestive enzymes and bile. 2. Absorption of useful nutrients from digested food into blood vessels of intestine. 3. How does liver help in digestion? Ans: Liver helps in digestion by secreting bile into small intestine. Bile digests lipids into fatty acids. 4. Heart burn is an acid indigestion. Justify the statement. Ans: Heart burn is an acid indigestion because it happens when acid from stomach get through the esophagus. This stomach acid irritates the esophagus and cause heart burn. 5. Doctors advice to have fiber rich diet. What would happen, if one’s diet has low in fiber? 11 Teacher Resource Pack Guide Science 7 Ans: If one’s diet has low fiber content, it will cause more absorption of water from digested food into blood thus leading towards constipation. Lesson 5 Topic: (1.6: Human respiratory system) Teaching objectives: ⦁ Explain the functions of respiratory system. ⦁ Explain the component (organs) with location required in respiratory system. ⦁ Demonstrate understanding of respiratory system by creating model. Key vocabulary: Breathing, cellular respiration, larynx, trachea, bronchi, lungs, diaphragm, alveoli. Materials required: ⦁ Board (white/black), marker/chalk, CSS-Science-7, Models/Charts of respiratory system. Teaching notes: The respiratory system is the group of organs that takes oxygen inside and expels out carbon dioxide. The oxygen thus inhaled is utilized in respiration process to provide energy. Breathing: It is the inhalation of oxygen and exhalation of carbon dioxide from the body (produced as a result of respiration). Respiration: It is the production of energy using oxygen from breathing and glucose from digestion. Breathing is just responsible for gaseous exchange. The first destination of inhaled air is nostrils. Here air is heated according to body’s internal temperature. Mucous and hair of nose also clean this air from bacteria and dirt. From nostrils. air moves towards larynx by passing through pharynx. From pharynx it moves into trachea which in chest region divides into two branches in left and right directions which are called bronchi. Bronchi open into lungs. Through these tubes air reaches into lungs which are the final destination of air. In lungs bronchi divides into small sacs called alveoli. Here oxygen from air is transferred to blood by absorption in blood capillaries wrapped around alveoli. The diaphragm controls the movement of lungs. Introduction: Ask students take a deep breathe in and then out. Tell them, you just successfully operated the respiratory system, your body’s mechanism activated for gaseous exchange. Ask them, they do not have to keep in mind it every time. It happens automatically. Tell them, they are going have a journey of respiratory system. When you think of respiratory system, you typically think of only lungs expanding and relaxing during breath. There is actually much more to the respiratory system than just the lungs, though they do essentially serve as the grand central station of breathing. Ask some questions; What they know about respiratory system? Why do all living things need to undergo gaseous exchange? What is the job of respiratory system? Is there any other organ system involved in respiration? What is the purpose of that system? What is the purpose of respiratory system? Teaching phase: The teacher will conduct the activity of purposeful breathing to attempt to envision what is happening as the air goes in and out of lungs as done before. The teacher will act 5-7 minutes meditation and will ask students to follow. The teacher will ask student to focus on breathing movement. It will draw the student’s attention to their breathing by taking consecutive deep inhalations and forcefully exhalations. Explanation of respiratory system: Then explain the topic i.e. components of breathing system. Explain each component, take help from models and then draw it on board. Start the 12 Teacher Resource Pack Guide Science 7 lesson from first respiratory organ i.e. nose. Explain it and let it revise by students. The teacher may pose some questions as well. Ask students draw the diagrams of respiratory system. Assessment: After explaining the complete lesson distribute the worksheets among students and give them some time to solve it. Then conduct a discussion on the following questions. The Structures of the Respiration System: 1. Why do we breathe? 2. How do we breathe? 3. Can we control our breathing? Explain your answer. 4. Can we survive if we are not breathing? Explain your answer. Discuss the answers of given questions. Closure: The students will demonstrate what they have learned randomly, by a small writing activity. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ List 5 of the most significant things that you learned today about the structures of the respiratory system. 1. __________________________________________________________________________ 2. __________________________________________________________________________ 3. __________________________________________________________________________ 4. __________________________________________________________________________ 5. __________________________________________________________________________ Home work: Ask the following questions for home work. Q. Describe the structure of respiratory system. Lesson 6 Topic: (1.6.2: Respiration in humans and its mechanics) (1.7: Breathing and burning processes) Teaching objectives: ⦁ Explain the process and purpose of respiration. ⦁ Explain the usefulness of respiration. ⦁ Explain the differences between breathing and burning. Key vocabulary: Respiration, ATP, burning, enzymes. Teaching points: Respiration is a process of energy production. This process uses Oxygen and glucose to produce energy, along with carbon dioxide and water. These are by-products of respiration. We exhale this carbon dioxide during breathing and water is either utilized for cell activities or is excreted out. The process of respiration takes place in mitochondria. Oxygen to be used in respiration is inhaled from air through breathing. Whereas, glucose is produced as a result of digestion. Both things are provided to mitochondria where energy is produced. The equation for respiration is: C6H12O6 + 6O2 6CO2 + 6H2O + ATP Topic: (1.7: Breathing and burning processes) The process of breathing is similar to burning process because the purpose of both process is to produce energy. But there are some differences in both processes. 13 Teacher Resource Pack Guide Science 7 The raw materials of both processes are different. Respiration uses glucoses and oxygen while burning use fuel (coal, wood, oil, gas) and oxygen. Respiration continues all the time in body while burning happens in atmosphere and when the raw materials and temperature required for ignition are available. There are several enzymes that control the respiration process while burning is controlled by amount and quality of raw materials. Introduction: Ask some questions to refresh the knowledge of students. For example: How is energy produced in animals? Why do we breathe more rapidly and more frequently after exercise? How does O2 and CO2 move in and out of cells? When you exercise you breathe in and out more frequently, why does this happen? Write students responses on board. Ask students if they link answers together to suggest the topic for today’s lesson. In case, students could not guess the topic, tell them, all the answers are related to the first question i.e. How is energy produced? The production of energy is the duty of respiration process. And today they are going to explore this very important process i.e. respiration and then they will compare the two energy producing process i.e. respiration and burning. Explanation and development: Then explain the topic. Activity: After that, write the following words on the board. Carbon dioxide, oxygen, energy glucose. Also draw a T-Chart on board. Ask students to write the same on their note books. Reactant Products Guide students to classify each substance in the list in the respective column of T-Chart. Give students some time. Then complete the table on board by student’s responses. Ask students: i. What happens to carbon dioxide thus produced? ii. What is the use of energy thus produced? iii. Which organ system is responsible for glucose production? Then, explain their answers by themselves. To teach the difference between respiration and burning, display the pictures of coal burning and cellular respiration. Respiration Draw a T-Chart on board below the picture as: Respiration 14 Coal Burning Burning Teacher Resource Pack Guide Science 7 Ask students to identify what is happening in picture 2 i.e. coal burning. Ask them questions such as: i. How does coal burn? ii. What does happen when coal burn? iii. Which things are required to burn coal? iv. Can the burning also happen inside the body? v. In which form burning releases energy? vi. Can we control the fire? How? Write the answers of these questions in respective column of the T-Chart. Then compare these answers with that of respiration process. Write students responses on board. Then complete the table by yourself by taking responses from students. Respiration Burning Occurs at cellular level Occurs in atmosphere Complete in several steps One step process Slow Fast Occurs at normal temperature Occurs at high temperature Controlling factor: enzyme Controlling factor: Amount and quality of reactant Energy form: ATP Energy form: heat Closure: Revise all the main points from board. Ask few students to read the lesson from CSS Science book – 7 with correct pronunciation. Assessment: Distribute the following work sheet and ask students to complete it. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ Write the similarities and differences of burning and respiration in following Venn diagram. Burning Respiration Home work Assign following question as Home work i. Describe the process of respiration. ii. Differentiate between respiration and burning. Lesson 7 15 Teacher Resource Pack Guide Science 7 Topic: (1.8: Common diseases of respiratory system) Teaching objectives: ⦁ Explain the diseases of respiratory system. ⦁ Describe the causative agents and preventive measures of respiratory diseases. ⦁ Explain the differences between breathing and burning. Key vocabulary: Asthma, inflammation, Pneumonia, wheezing, streptococcus pneumonia, mycobacterium tuberculosis, antibiotics, passive smoking. Material required: Board (White/Black), Marker/Chalk, CSS Science book – 7, regular drinking straw (one for each student), thin straw (coffee stirrer) timer, balloons. Teaching notes: Some of the common respiratory diseases are asthma, pneumonia, tuberculosis and lung cancer. Asthma is a chronic disease. A chronic disease last for 3 months or more. It is long lasting in its effects. It can’t be prevented by vaccines or cured by medicines. Chronic diseases are just controlled not cured. So, asthma can’t be cured by medicines. In asthma, bronchial tubes become inflamed and thus became narrow. As these tubes pass air into lungs, so, it becomes difficult to breath out and in. So, the patients suffering from asthma experience intense coughing, wheezing and chest tightness. Asthma may develop genetically (from one generation to another) or environmentally. The toxic fumes of traffic smoke, dust particles from construction, mining and chemical industry cause to inflame the bronchial tubes. Pneumonia is a condition in which bronchioles and alveoli become inflamed. It happens due to a bacterium named as streptococcus bacterium. Pneumonia can be diagnosed by its symptoms i.e. dry cough, chest pain, fever and trouble in breathing. If both lungs affect, it is called double pneumonia. It is a worse condition. Tuberculosis is generally known as TB. Bacterium mycobacterium tuberculosis enters into lungs and irritates alveoli. The major symptoms of TB are coughing, weight loss, fever, sweats at night, feeling chill, etc. TB can be prevented to spread by proper care. Use of mask while interacting affected person proves much effected. When the cells of lungs continue to divide uncontrollably, A bundle of cells forms which is called tumor. That’s lead to develop cancer in lungs. This process is known as metastasis. This tumor formation is caused due to smoke of cigarette. Chemotherapy is used as its treatment. Introduction: Explain the class that they will be starting the lesson with an experiment. Pass out one large straw to every student in the class room. Ask students to place the straw in their mouth and pinch their noses. The students are to breathe through this straw for 30 second (at rest). Instruct the students to stop the activity if they feel difficulty in breathing. Ask the students to write their reaction and observation obtained from this activity. e.g. How did breathing in this manner make them feel. (1 minute to free write). Ask students again to place large straw in their mouths, pinch their noses and jog in place for 30 seconds using the straw only. Do the same activity with coffee stirrer. Ask students what they think these activities taught. The first activity simulates the breathing experience by a smoker. The second activity simulates how it feels like to live with lungs cancer. Ask: How many of you know someone who is living with chronic lungs disease. Help students to deduce the answer, by using the observations learned from above performed activities. Development: Divide students into four groups. Assign one respiratory disease to each group. Provide index card to each group. These cards would be titled as: What the disease is? Symptoms Causes Preventive measures. 16 Teacher Resource Pack Guide Science 7 Ask students to prepare their topic from CSS Science book 7. The teacher will roam in class; talk with students about their assigned disease. After they have done, teacher will call each group in front of class and the group will present its topic. After students have done, the teacher will him/herself explain the disease. Ask some questions to evaluate students understanding. The teacher will also note down the key points on board. Summary/Closure: Then, revise all the main points from the board. Read lesson from CSS book – 7 with correct pronunciation. Home work: Assign the following question as home work. Write a brief note on various respiratory disease. The note must include: 1. Introduction of disease 2. Symptoms of disease 3. Causes of disease 4. Preventive measure of disease Assessment: Distribute the worksheet to the class and ask them to solve it. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ 1. Write down the causative agents of tuberculosis and pneumonia. Ans.__________________________________________________________________________ 2. What happens to bronchial tubes during asthma? Ans.__________________________________________________________________________ 3. How dose smoking affect the respiratory system? Ans.__________________________________________________________________________ Test Exercise – 2 A. 1. Choose the correct answer and fill the circle. Teacher Sara is showing picture of sound box in humans to the class. Which scientific term will she use for this? tongue larynx pharynx trachea 2. Which of the following is an organ which help in respiration? diaphragm liver heart stomach 3. Amjad is drawing air sacs in lungs on a chart paper. What will he label it? trachea diaphragm bronchioles alveoli 4. This is not a respiratory disease: asthma ulcer pneumonia tuberculosis 5. Choose the leading cause of lungs cancer from following: poor diet polluted air smoking tumor formation B. Answer the following questions briefly. 1. Differentiate between larynx and pharynx. Larynx Pharynx Larynx is a passage for air into lungs. Pharynx is a passage for food into stomach 2. Left lung is smaller than right lung. Justify the statement. Ans: Left lung is smaller than right lung because left lung has two lobes while right lung has three lobes. Also that left lung has to accommodate the heart as well. 3. How will you differentiate inhalation from exhalation? Ans: Difference between inhalation and exhalation is given below: 17 Teacher Resource Pack Guide Science 7 No. Inhalation No. Exhalation i. Inhalation is a process of breathing in air i. Exhalation is a process of breathing out air (oxygen). (carbon dioxide). ii. During inhalation, intercostal muscles and ii. During exhalation, intercostal muscles and diaphragm contracts and moves downward. diaphragm relax and move upward. 4. What is diaphragm? Ans: Diaphragm is a dome shaped muscle at the bottom of the lungs. It controls the process of breathing and separates the chest from the abdominal cavity. 5. Passive smoking leads to lungs cancer. How? Ans: Passive smoking leads to lungs cancer if it continues for long term. In passive smoking, the smoke of cigarette enters into lungs and destroys lung cell as same as in case of active smoking. Review Exercise A. 1. Choose the correct answer and fill the circle. Where does the emulsification of fats take place? in mouth in stomach in small intestine in large intestine 2. Which biomolecules are digested through hydrochloric acid? proteins fats carbohydrates vitamins 3. This is NOT an organ to serve as digestive gland: liver gall bladder pancreas oesophagus 4. Name the starting point of small intestine: duodenum jejunum Ileum rectum 5. An enzyme to digest carbohydrates is: pepsin amylase lipase pepsinogen 6. Choose the most important organ in human respiratory system: lungs larynx diaphragm epiglottis 7. Ali wants to label the energy released from respiration. What scientific term will he use for this? heat light ATP NADH 8. The main cause of pneumonia is: Streptococcus pneumonia Escherichia pneumonia Chrococcus pneumonia Pseudomonas pneumonia 9. What happens to diaphragm during inhalation? it contracts it relaxes it moves upward it expands 10. The site for cellular respiration is: cytoplasm Golgi apparatus mitochondria nucleus B. Answer the following questions briefly. 1. What is the function of saliva? Ans: Functions of saliva are as follows: a) It moisten food for easy swallowing. b) It contains salivary amylase that digest the carbohydrates. 2. Name the causative agent of tuberculosis. Ans: Causative agent of tuberculosis is mycobacterium tuberculosis. 3. Epiglottis serves in both digestive and respiratory system. How? Ans: Epiglottis is present on the mouth of larynx and pharynx. It directs air into larynx and food into pharynx. 4. Differentiate between breathing and burning. 18 Teacher Resource Pack Guide Science 7 Ans: Difference between breathing and burning is given below: No. Breathing No. Burning i. The breathing is a part of the human respiratory i. The process of burning occurs in the atmosphere. system. Respiration occurs at cellular level. ii. This process has several steps. ii. This is only one step process. 5. Double pneumonia is caused when pneumonia is severe. How? Ans: When pneumonia gets severe, both of the lungs become infected. This situation is called double pneumonia. 6. How does the physical digestion help in chemical digestion? Ans: In physical digestion larger food bites break down into smaller particles. These smaller particles of food are easy to swallow and assimilate in chemical digestion. Therefore, physical digestion help in chemical digestion. C. Answer these questions in detail. 1. Describe various components of human digestive system. Ans: Human digestive system: The human digestive system is an organ system designed uniquely to convert the food we eat into the nutrients. The body uses these nutrients for energy and growth. Components of digestive system: Food entered in the mouth passes inside the body through a long tube called alimentary canal. The alimentary canal is composed of mouth, salivary glands, tongue, teeth, throat, pharynx, oesophagus, stomach, pancreas, gall bladder, small intestine, large intestine and anus. These components of digestive system are described as follow: Mouth (oral cavity): The starting point of the digestive tract is mouth where physical digestion begins. 32 teeth break the food into smaller pieces by cutting and grinding the food. Many papillae are present on the upper part of tongue to grip the food. The tongue also helps to push the food toward the throat for swallowing. Saliva also mixes with the food to moisten it and begins the digestion of carbohydrates (starch) in the mouth. The body also uses saliva to lubricate food as it has to pass through the alimentary canal. This will change the food into a form that our body can absorb and use. Throat (pharynx): The throat which is also called pharynx, is the next destination for the food. Food travelled from here is shifted to the oesophagus (swallowing tube). Throat contains the epiglottis; a flap of tissues that acts as an opening to route the food to oesophagus. Oesophagus: The oesophagus is a tube that starts below the pharynx and extends to the stomach. There is peristalsis, a series of contractions, through which the oesophagus sends bolus to the stomach. 19 Teacher Resource Pack Guide Science 7 Stomach: “The stomach is a sac-like organ that has strong muscular walls”. The stomach acts as mixer and grinder after having the food. It secretes the hydrochloric acid, gastric juices and powerful enzyme (pepsin, inactive form: pepsinogen) that helps in continuing the breaking down of food. The food, now, has been changed in the form of liquid paste ready to leave the stomach. Small intestine: The destination of food next to stomach is small intestine. It is a loosely coiled long tube present in the abdomen. Its length is about 20 feet. Two purposes are served here. First, food is broken down by using digestive enzymes and bile. Second, useful nutrients are absorbed here. The digestive enzymes are released by the pancreas while the bile is provided by the liver. Bile is a compound that contributes in the digestion of fat. Peristalsis also helps to carry the food in this organ. There are three parts in small intestine: duodenum, jejunum and ileum. Duodenum is responsible for the process of breaking down food. Jejunum and ileum are responsible for the absorption of nutrients i.e. carbohydrates, proteins and fats in the blood. Large intestine (colon): After small intestine, the remaining food which has now become stool is transferred to large intestine. It is a five to six feet long muscular tube. The first part of the large intestine is caecum and the last part is rectum. The peristaltic movements facilitate the movement and transference of stool into and out of the colon. The stool is first converted into a liquid form and then changes in solid form. The water is totally removed from the stool here. The stool itself is mostly the food remains and bacteria. It defecated (excreted) out of the body through anus which is the last part of the digestive tract. It normally takes about 36 hours to get out of the body through the large intestine. Liver, gall bladder and pancreas: Liver, gall bladder and pancreas are digestive glands that help in the digestion of food by releasing different secretions. “The liver is the second largest organ in the body that weighs about 3 pounds”. It is located below the diaphragm, at the right side of the stomach and above small intestine. It produces and secretes bile into the small intestine by the liver. “The gall bladder is a pear-shaped small sized organ located just below the liver”. The gall bladder is used to store and recycle the excess amount of bile from the small intestine. This stored bile is reusable for the digestion of upcoming meals. “The pancreas is a large gland located just below the stomach”. Its length is about 6 inches. Its head is connected to the duodenum and the tail is pointed to the left side wall in the 20 Teacher Resource Pack Guide Science 7 abdominal cavity. The digestive enzymes are secreted into the small intestine by pancreas to accomplish the chemical digestion of food. 2. Write a note on importance of digestion. Ans: Digestion is the process of conversion of the large and complex pieces of food into small and simpler components. The food is digested in two steps: mechanical and chemical digestion. Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces. This step begins with the chewing of food by teeth and continues through the mixing of food by the peristalsis in stomach and intestines. Chemical digestion is the breakdown of larger food molecules into smaller ones. It also begins in the mouth by the action of are (salivary amylase) present in saliva that splits the complex carbohydrates into simple carbohydrates. The chemical digestion continues in stomach with the help of hydrochloric acid and enzyme pepsin. Most of the chemical digestion takes place in the small intestine with the action of pancreas. The pancreas secretes pancreatic juice which digests carbohydrates, lipids and proteins into monosaccharaides, fatty acids and amino acids respectively. Bile (from the liver) also facilitates the chemical break down of fats into smaller molecules. Importance: The breaking down of food into useful nutrients is carried out by digestion. The body uses these nutrients for energy and growth. When anyone eats food (grains, meat, fruits and vegetables), it is not in a form that body can use it as energy source. It is necessary to change the food into smaller molecules of the nutrients, so that the blood may carry and absorb them to cells throughout the body. So, we can say that digestion is an important process for our survival. 3. How does digestive system help in the digestion of various kinds of foods? Ans: Digestion of various kinds of foods: Our diet contains different kinds of nutrients i.e. carbohydrates, fats, proteins etc. All this food is converted into the useable form through the process of digestion. Following are the enzymes that facilitate these conversions. Enzyme Occurrence Reacts with Final product Salivary amylase Saliva in mouth Carbohydrates Monosaccharides Pepsin Stomach Proteins Amino acids Hydrochloric acid Stomach Proteins Amino acids Bile Liver Lipids Fatty acids Pancreatic juice Pancreas Carbohydrates, Monosaccharides, amino acids proteins and fats and fatty acids 4. Identify the common disorders of the digestive system. List the factors that lead to constipation and diarrhea. Also describe the measures that can be taken to prevent them. Ans: Disorders of the digestive system: Following are the common disorders of the digestion: Diarrhea: “Diarrhea is an increase in the frequency of bowel movements”. This increases the looseness of stool. It is caused by increased amount of secretion of fluids into the intestine. It also reduces the absorption of fluid from the intestine. Symptoms associated with diarrhea include abdominal pain mainly cramping and vomiting. Constipation: “Constipation occurs when the bowel movements are tough or happen less often than normal”. It is the condition when the stool becomes harder and more difficult to pass out. The normal duration between bowel movements, changes greatly from one person to another. Heart burn: Heart burn (acid indigestion) results in the production of sensation of burning in stomach and the patient might feels sour taste in the mouth. The patient feels the symptoms more than two times in a week. Ulcer: Ulcer takes place when the internal lining of the stomach is damaged due to bacterial infections. It is caused by Helicobacter pylori. This bacteria transfer through spicy food. High stress levels also activate ulcer causing secretions. The severe side effects of some medicines (i.e. Aspirin) can also cause ulcer. Factors and preventive measures of constipation and diarrhea: 21 Teacher Resource Pack Guide Science 7 Factors leading to constipation: The factors that lead to constipation are: Poor diet, food containing animal fats (dairy products, meats and eggs) and low-fiber sugar (whole grains, fruits, and vegetables). Insufficient water intake Sometimes caffeine and alcohol induce increased excretion and urination of water. This causes the dehydration that ultimately leads to constipation. Measures for the prevention of constipation: To prevent the constipation: We should intake proper amount of certain foods and drinks. Proper exercise is also helpful. We should also eat high-fiber foods (raw vegetables, cereals, and fresh fruits). We should also drink at least eight glasses of water a day for being healthy. Factors leading to diarrhea: Diarrhea is usually caused by: Virus, bacteria and parasites Stress, anxiety Excessive alcohol intake, food allergy, appendicitis damage the internal lining of the intestines. Side effect of a medication for example antibiotics and antacid medicines (containing magnesium). Measures for the prevention of diarrhea: To prevent diarrhea: We should avoid eating the unhygienic food. We should only use purified water. We should eat only properly cooked vegetables and fresh fruits. 5. Explain the mechanism of cellular respiration in humans. Ans: Respiration in humans and its mechanics: Respiration is the production of chemical energy from the food molecules produced in digestion. As a result, carbon dioxide is produced that is breathed out of the body from the lungs. The digested food molecules (proteins, carbohydrates and fats) mix with the blood stream. As a result of breathing, oxygen reaches to the lungs where it is absorbed by the blood. Both the food molecules and oxygen are transferred to body cells. Here, this oxygen is then used by the mitochondria to breakdown the food to produce energy in the form of ATP. This energy is utilized to do work. Water and carbon dioxide are also produced and released out of the body cells in the process of cellular respiration. Unit # 2 TRANSPORT IN HUMANS AND PLANTS Lesson 1 Topic: (2.1: Transport system in humans) (2.2: Circulatory system and its components) (1st half) Teaching objectives: ⦁ Explain how material i.e. blood, gases etc. is transported in humans. ⦁ Explain the function of circulatory system. ⦁ Explain the components of circulatory system. Key vocabulary: Transport system, blood, pH, red blood cells, white blood cells, platelets, arteries, veins, and aorta. Materials required: ⦁ Board (White/Black), marker/chalk, CSS – Science Class – 7, Model / chart showing the structure of heat, chart of circulatory system. Card board/hard chart, red and blue glaze paper. Teaching points: A system of human body that transports materials i.e. oxygen, food (glucose), carbon dioxide, energy from one organ to another is known as transport system. In humans and other higher animals, blood circulatory system performs this function. 22 Teacher Resource Pack Guide Science 7 Blood receives oxygen from lungs and nutrients from digestive system and carries them to every cell of our body. In this way, circulatory system provides nutrients and energy to the body. In plants, this purpose is fulfilled by vascular system by xylem and phloem. These two long tubes receive water from roots and food from leaves and transfer these to every part of plant. The human circulatory system consists of heart, blood vessels i.e. arteries, veins, capillaries. Heart pumps the blood and blood vessels carry it to all body parts. Human heart is a strong muscular organ with no bone in it. It is present in chest cavity, at left side. The cavity where heart is present is filled with a fluid that protects it from outer injuries. This cavity is called pericardial cavity. To ensure protection and avoid abrasion with ribs and lungs, the heart is enclosed /covered by a doubly membrane protective layer which is called pericardium. Pericardium lubricates the heart and keeps it in accurate position. The heart has 4 chambers just like 4 rooms, each with specific function. The upper two chambers (left and right) are called auricles (sing. atrium) whereas the lower two chamber (left and right) are called ventricles (right ventricle, left ventricle). The upper chambers (auricles) are smaller than lower chambers (ventricles). These four chambers are separated by four valves. These valves act as door that regulate the blood movement. On the upper side of heart, aorta is present, which is the largest artery in human body. It receives blood from the body. The upper chambers (auricles) receive blood from the body and ventricles send blood out of the heart. The ventricles are connected to the arteries. Along the aorta, the largest vein named superior vena cava is present. It provides blood to right atrium. Introduction: As you are going to teach a new lesson, tell students briefly about the chapter. Then introduce the lesson you are going to teach. Show the chart of circulatory system to the class. Engage the students by describing how blood moves in the body and what it carries in it. Ask some questions that may guide students towards the today’s lesson. e.g. 1. Human need oxygen and food to live. Oxygen enters into lungs and nutrients are produced into stomach. How are these provided to all cells in the body? Which organs do you think are part of the transport system? Why some blood vessels blue and some are red? Is there any other body system involve or facilitate the transport system? Development: Then show the structure of heart and explain it step by step. When you explain any structure, draw it on board as well. Activity: 23 Teacher Resource Pack Guide Science 7 Work Sheet Name: __________ Class: __________ Label the given structure of heart. Roll Number: _________ Date: __________ How is heart protected from external injuries? The teacher can make the model of structure of heart in class. The teacher may ask to build the hearts model using match boxes instead of card board and label it properly. Distribute the following work sheet and students to solve it. Homework: Assign the following questions for home work. Define transport system in humans. Explain the structure of heart with well labeled diagram. Lesson 2 Topic: (2.2: Functions of heart, structure of blood vessel, functions of blood vessels) (2nd half) Teaching objectives: ⦁ Explain the functions of heart. 24 Teacher Resource Pack Guide Science 7 ⦁ Describe the structure and function of blood vessels. Key vocabulary: Oxygenated blood, deoxygenated blood, arteries, veins, capillaries, thin walled blood vessels, thick walled blood vessels, unidirectional blood flow. Materials required: ⦁ Board (White/Black), chalk/marker, CSS book – 7, model/chart of blood vessels. Teaching points: Heart is the main transport organ in human body. It regulates the supply of nutrients and oxygen throughout the body. Our heart receives deoxygenated blood (blue) from body parts and provides fresh oxygenated blood (red) to them. The four valves of heart keep the blood (oxygenated and deoxygenated blood) separate. Blood is oxygenated when it receives oxygen and is deoxygenated when it transfers its oxygen to body cell of all parts. Both type of blood are kept separate in heat by its chambers, to avoid mixing of both type of bloods. Blood when leaves the heart and when it is to enter into heart from body parts, it need transport/passage/paths. This passage is provided by blood vessels. Blood vessels are narrow tubes that form a network throughout the body. Just like water is supplied to every house in a big city. These blood vessels are of three types: i) Arteries ii) Veins iii) Capillaries Arteries are blood vessels that carry oxygenated blood to body parts from heart. When blood is pumped from heart into arteries, its pressure is high, so, to bear this high pressure, arteries have thick muscular walls. All the arteries arise from the biggest artery. i.e. aorta. Veins are blue in colour and carry deoxygenated blood. As the deoxygenated blood is at low pressure, there is no need to have thick walls. So, veins have thin walls. These vessels possess valves in them that prevent the back flow of blood. There is a connection between arteries and veins. This connection is a netted pattern of blood vessels that join arteries and veins. This netted pattern is called capillaries. Blood vessels not only supply the oxygenated blood to the body but receive deoxygenated blood from the body parts. Introduction: As students have learned about structure of heart, ask students some questions to refresh their knowledge and guide towards the current topic. e.g. What would happen if there is no pericardium around heart? What is the advantage of valves to body? After having answers to these questions, introduce the today’s lesson. Tell them first they will deduce the functions of heart from previous knowledge. Then, they will learn how blood is supplied to all body parts. Development/Activity: Draw the structure of human heart on board and ask students to draw it by themselves. After they have done, ask them to label it. Ask students what they think, how does a heart work. What is the function of aorta? (Supply oxygenated blood to the body). What would you expect to be happening if there would be no valve? (Exp. Ans: It would cause mixing of oxygenated and deoxygenated blood). After having answers of these questions ask them to deduce the functions of heart. Give 2 – 3 minutes to writer their answers. Then share some of the students’ answers with class. And explain it. Write key points on board. To teach blood vessels show students the picture of water supply within a city. Analogies this pipe network with blood vessels in the body. Then show the picture of blood vessels in body. Explain the three types of blood vessels one by one. After explaining the structure of blood vessels, ask students to deduce the function of blood vessels. As done for the functions of heart. Closure: Read the lesson from CSS-Science book for Class 7, with correct pronunciation. Homework: Assign the following questions as home work. 25 Teacher Resource Pack Guide Science 7 Describe the structure and functions of blood vessels. Lesson 3 Topic: (2.3: Working of the circulatory system) Teaching objectives: ⦁ Make students understand how blood becomes oxygenated and deoxygenated. ⦁ Make the students able to understand the flow of blood in the body. Key vocabulary: Oxygenation, deoxygenation, pulmonary vein, contraction, relaxation, pulmonary artery, back flow, semilunar valve. Materials required: ⦁ Board (White/Black), marker/chalk (black, red, green, blue), CSS – Science Class – 7, Model/Chart showing the blood circulation. Teaching points: This lesson is about the working of circulatory system. The part of the heart and blood vessels that appear in blue colour contains deoxygenated blood where as the red part of heart and blood vessels contain oxygenated blood. Oxygen rich blood is present in left side of the heart (atrium and ventricle). Whereas deoxygenated blood is present in right side of the heart (atrium and ventricle). First, blood needs to get oxygen. So this, blue blood moves towards lungs in pulmonary artery from right atrium and get oxygen that is inhaled during breathing. After getting oxygen, blood come back to heart in pulmonary veins into left atrium. It is to be noted that while moving in and out of lungs the function of arteries and veins is altered. The oxygenated blood is sent to left ventricle from left atrium by bicuspid valve. Then, heart pumps (contracts) and this oxygenated blood is sent to aorta from where it is supplied to all the body parts. In this way oxygen and food is transported from blood to body cells. When oxygen is transferred into cells, nitrogenous waste and carbon dioxide is released into blood. This is the reason, the blood becomes blue and is termed as deoxygenated. This waste carrying blood is moved towards kidneys. Kidneys remove nitrogenous waste through blood. This blood is then collected through veins and is returned to heart through superior vena cava, which is then moved back to lungs for oxygen. Thus the cycle continues. Introduction: Ask some questions to refresh the students’ knowledge and to guide them towards todays lesson. a) How does blood get oxygen? b) Why does the blood looks blue? c) Arteries are specified for oxygenated blood but why does pulmonary artery looks blue? After having answers from students, introduce the today’s topic. Tell students they one going to learn how circulatory system works. Development / Activity: In order to make students understand, draw the basic structure of heart as shown in the figure below. 26 Teacher Resource Pack Guide Science 7 Represent the inlet and outlets of deoxygenated blood with blue arrows as per figure. Draw inlet and outlet of oxygenated blood with red arrows (as per figure). Draw the heart chambers with red arrows. Then explain the flow of blood as given in teaching notes. Explain them that blood flows the heart in 12 easy steps. Blood must flow through 6 areas on the right side and 6 areas on left side. As follows: Right side Left side Superior vena cava Pulmonary vein Right atrium Left atrium Tricuspid valve Bicuspid valve Right ventricle Left ventricle Pulmonic valve Aortic valve Pulmonary artery Aorta Right side of the heart: Right side blood flow aims to get the blood to lungs for oxygen. Then, explain the each station in right side and left side. Study tip: The students can learn the position of pulmonic artery by relating the function to its position i.e. right side goal is to get blood to lungs. So, pulmonary artery will be drawn at right side. In the same way explain the left side stations. As the goal of left side to transport blood to body organs. Study tip: In order to memorize that whether blood enters the bicuspid valve first or tricuspid valve, ask students to memorize the following mnemonic line. “First always try (tri), before you buy (bi).” By remember this phrase; they will remember that the tricuspid (try) is before the bicuspid (buy) valve. To remember which chamber is at upper end remember that A comes before V in alphabets. So, A for atrium is at upper side and V for ventricle is at lower side. Closure: At the end of the lesson, revise all the main points from board. Assessment: Distribute the following work sheet and ask students to solve it. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ 1. Describe the route of oxygenated blood in the heart. Ans. _________________________________________________________________________ 2. How does blood becomes deoxygenated? Ans. _________________________________________________________________________ 3. Describe the function of bicuspid and tricuspid valves in heart. Ans. _________________________________________________________________________ Lesson 4 Topic: 27 (2.4: Scientific developments for dysfunctional body parts) Teacher Resource Pack Guide Science 7 Teaching objectives: ⦁ Explain the students that dysfunction in any part of heart can be corrected by scientific advancement ⦁ Explain some technological advancements regarding heart problems. Key vocabulary: Dysfunction, electro-cardiogram, angioplasty, angiography, x-ray examination, open-heart surgery, balloon (stents) pacemaker. Materials required: ⦁ Board (White/Black), marker/chalk, self-made models of stents, pace maker. Introduction: Ask some questions that may engage and guide students towards today’s topic e.g. What happens when any artery or vein may block due to any reason? How would you describe a heart attack? Have you ever seen/met a person who have recently experienced heart attack? How did he recover? Which treatment he received in hospital? Do you know any technology specific for heart patients? After having answer from students, introduce the today’s lesson. Tell students, they are going to learn about technologies that are helpful for treatment of heart diseases. Explain students that sometimes high fat content in blood, high sugar content may accumulate in blood vessels and make its passage narrow. Sometimes, due to intense feeling i.e. anger, tension, etc. pressure of blood may increase or veins and arteries may block due to clotting in all such cases; functioning of heart disturbs and in severe cases it may lead to heart attack, hemorrhage, etc. Then, the question arises, how you could treat it. Science has developed many technologies not only to recover the problem but also to diagnose. Some of these technologies will be discussed in today’s class. Development: Then the teacher will paste the heart’s model made of hard chart paper on board. Make and paste any artery to the heart’s structure. Now show blockage in artery. Tell students that when they eat too much fried and junk food, have sweets and cola drinks, our blood become rich in fat and glucose content. These fat content (cholesterol) deposit in arteries and block the flow of blood. Blockage of any artery would cease the blood supply to its destined organ. Science has developed techniques to diagnose such conditions. One of them is angiography. Angiography is an x-ray technique. After showing students blocked artery. Ask them: 1. What do you suggest the cure/treatment for this blocked artery. (Expected Ans. (i) remove clot/hindrance (ii) dilate artery). If any answer include the second option, extend it to angiography. Then explain the complete procedure of angiography. Tell them it is a technique that compress the cholesterol deposit and make passage available for blood to flow. First, a stent (balloon) is inserted into target artery through a carrier called catheter. Second, catheter is removed out. Thirdly, balloon expands and widen the passage for blood. The teacher will show the procedure to class with catheter made of had white chart and insert it into the blocked artery. In the same way, the teacher would explain other technologies. It is recommended that models of these technologies should be prepared before class. Closure: Revise all the technologies from key points written an board. Read the lesson from CSS Science book for class-7 with correct pronunciation and explain any term if remained unexplained. Assessment: Distribute the following work sheet to the class and ask them to solve it. Then 28 Teacher Resource Pack Guide Science 7 discuss the question of work sheet in class, the same day or the next day. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ 2. When is open heart surgery done? Ans. _________________________________________________________________________ 3. Describe the procedure of angioplasty. Ans. _________________________________________________________________________ 4. What would you recommend when someone’s heart get failure? Ans. _________________________________________________________________________ Home work: Assign the following topics as homework. 5. Describe the conditions when angiography and bypass surgery is done. 6. Write a note on artificial value, artificial pacemaker and heart transplantation. Test Exercise – 1 A. 1. Choose the correct answer and fill the circle. Choose an appropriate scientific term for circulatory system: lymphatic system cardiovascular system cardio-pulmonary system lympho-vascular system 2. The composition of heart is: skeletal muscles smooth muscles cardiac muscles skeletal tissues 3. The largest vein of the body is: superior vena cava inferior vena cava pulmonary vein aorta 4. Maria wants to tell the class about valves. How will she define the term? the special openings through which atria are interconnected for blood transfer. the special openings through which ventricles are interconnected for blood transfer. the special openings through which heart chambers are interconnected for blood transfer. the special openings through which heart chambers are interconnected for gaseous exchange. 5. The blood that veins receive from the body is: oxygenated and reddish oxygenated and bluish deoxygenated and reddish deoxygenated and bluish B. Answer the following questions briefly. 1. Define circulatory system. Ans: Circulatory system is a system of organs to transport blood, oxygen, nutrients and other materials to all body parts. 2. Heart is composed of chambers. Name these chambers. Ans: Heart has four chambers. Their names are: i. right atrium ii. left atrium iii. right ventricle iv. left ventricle 3. How is backflow of blood prevented in heart? 29 Teacher Resource Pack Guide Ans: 4. Ans: 5. Ans: Science 7 Backflow of blood in heart is prevented by valves present in veins. Define bypass surgery. Bypass surgery is a surgical procedure performed to open a blocked coronary artery. How does angiography help to treat the blockage of artery? Balloon used in angiography widens the narrowed artery due to deposition of cholesterol. Lesson 5 Topic: (2.5: Disorders in circulatory system due to diet ) Teaching objectives: ⦁ Explain that diet affect our circulatory system. ⦁ Explain that due to improper diet many diseases occur. ⦁ Describe the diseases and their causes that occur due to inefficient diet. Key vocabulary: Saturated fat, high blood pressure, diabetes, anemia. Materials required: ⦁ Board (White/Black), marker/chalk, CSS-Science-7. Teaching Points: A saturated fat is a type of fat obtained from animals. It is solid at room temperature. Some examples are butter, meat fat, and coconut oil. Such fats raise the level of cholesterol in the blood. The food that contains high level of saturated fat, tend to increase the level of fat content in blood. In the presence of high fat content in blood, blood finds resistance to flow easily. With passage of time, this fat begin to deposit in blood vessels, resultantly blood vessels became narrow for blood flow. Blood passes through these narrowed vessels, it exerts more pressure on walls. This condition if lasts for long time, cause heart attack. 1. Diet deficient in iron cause deficiency of red blood cells (because red blood cells contain iron). These red blood cells carry oxygen to body cells. Thus, their deficiency causes oxygen deficiency which in turn will lead to weakness. As oxygen is necessary for respiration process to produce energy. 2. Diet containing high glucose level also damage blood vessels. 3. Blood vessels contract and relax to control blood pressure. More contraction in the blood vessels, higher the blood pressure, higher the blood pressure for long time leads to heart attack. Introduction: 1. Begin the lesson by asking student to identify the location of their heart and its functions. 2. Tell students about the importance of a healthy heart. 3. Explain that without proper care, and with poor diet diseases can occur that they will explore in this lesson. 4. Then select a volunteer to read the lesson from CSS-Science-7 book. Development: Pose some questions to check what they have understand e.g. 1. Why is it not recommended to have junk food? 2. Can you think of some foods that provide iron? 3. How does sugar affect our circulatory system? Now divide class into three groups. Assign one disease to each group. Ask them to prepare their topic from book. Teacher should mingle with students and discuss topic with students. Then ask students to come in front of class and present their topic. When students have done with their turn, explain the diseases yourself one by one. Summary: Revise all the main points from board. Assessment: Distribute the worksheet and ask students to solve it. 30 Teacher Resource Pack Guide Science 7 Work Sheet Name: __________ Class: __________ 1. Name the factors that may cause high blood pressure. Roll Number: _________ Date: __________ Ans. _________________________________________________________________________ 2. Why is iron rich food necessary for circulatory. Ans. _________________________________________________________________________ 3. How can you control diabetes? Ans. _________________________________________________________________________ Home work: Assign the following question for homework. 1. Describe some disorders of circulatory system that result due to improper diet. Lesson 6 Topic: (2.6: Transport system in plants) Teaching objectives: ⦁ Explain students that plants also transport material. ⦁ Explain that how plants transport water and food. Key vocabulary: Roots, stems, xylem, phloem, osmosis. Materials required: ⦁ Board (White/Black), marker/chalk, CSS-Science-7. Chart / model showing structure of xylum and phloem. Introduction: The teacher may ask following questions for checking previous responses. 1. Where does photosynthesis take place in plants? 2. How do water and minerals reach leaves? 3. How does prepared food reach other parts of plant body? 4. What would happen to plant when soaked in excess water? 5. Where does this excess water go? After having answers from the following questions, the teacher will introduce the today’s lesson and tell them that today they are going to study about xylem and phloem that transport the materials like food and water. Development: Show students the chart / model of xylem and phloem. Tell them about the structure and function of these two vessels. Relate them with blood vessels. As blood vessels transport oxygen and food to body parts in the same way xylem transports water and phloem transports food. Tell them that xylem and phloem are present in roots and extend up to leaves. Discuss the process of transpiration and translocation. Explain them how roots absorb water and transfer it to the upper most leaves. Activity: The teacher can conduct the following activity to visualize the process of transportation in plants. What to do: 1. Cut the 3 growing branches of rose plant. (It is recommended to use cerel plant. Cerel plant has off white Stem so the transport of colour is more obvious. You can use motia flowers as well). 2. Mix the 3-4 drops of food colour in water taken in a beaker or pot. (One colour in one beaker) Mix it well. 3. Place one stalk in one beaker and stay it undisturbed at a lighted place. 31 Teacher Resource Pack Guide Science 7 4. The next day you will observe and let students to observe the stalk. White flowers have taken the colour of water. 5. Tell students the stalks have absorbed water from xylem, this xylem tube extends to leaves, thus water moves along with xylem vessels. Explain them that capillary action and transpirational pull help water to move upward. Summary: Revise all the main points from board. Read the lesson with correct pronunciation. Assessment: Distribute the worksheet among students and ask them to solve it. Work Sheet Name: __________ Roll Number: _________ Class: __________ Date: __________ 1. Indicate whether the rate of absorption of water from soil through root hairs increase or decrease a) After a heavy shower ………………………… Ans. _________________________________________________________________________ b) In a dry soil ……………………………… Ans. _________________________________________________________________________ 2. How does water enter root hairs? Ans. _________________________________________________________________________ 3. Describe the rote of xylem for water transportation. Ans. _________________________________________________________________________ 4. Why is water necessary for plants? Ans. _________________________________________________________________________ Test Exercise – 2 A. 1. 2. 3. 4. 5. B. Choose the correct answer and fill the circle. What will be the possible outcome of clogging of the arteries that feed the heart? anemia heart attack asthma brain hemorrhage Deficiency of which of the following mineral can lead to anemia? calcium potassium iodine iron Teacher Sara says: "The water molecules move from an area of higher concentration of water to an area of lower concentration of water through cell membrane". What is the process? diffusion osmosis transpiration evaporation Through which of the following parts, food from leaves is provided to rest of the plant? epidermis root hair xylem phloem Name the adjacent part of stoma? guard cell stomata mesophyll chloroplast Answer the following questions briefly. 32 Teacher Resource Pack Guide Science 7 1. Define tertiary roots. Ans: The roots that arise from the secondary roots are called tertiary roots. 2. How does xylem help in water transport? Ans: Xylem tubes are present in roots and extend up to leaves by passing through stem. Xylem tubes in roots suck water from soil by diffusion and transfer it to the upper most leaves by capillary action and transpiration pull. 3. Can you replace cuticle with Vaseline? Ans: No, Vaseline can’t be used instead of cuticle because it do not has pores and will cover the stomata thus exchange of gases would be ceased. 4. What is the role of stomata in leaves? Ans: Stomata are present in leaves. They regulate the exchange of gases by opening and closing guard cells. 5. How is transport system in lower plants different from that of higher plants? Ans: Transport system in lower plants is different from higher plants as lower plants lack the proper transport vessels i.e. xylem and phloem that are present in higher plants. In lower plants, the whole plant absorb water and mineral directly from environment. Review Exercise A. 1. Choose the correct answer and fill the circle. The Lub-dub sound felt from inside the left side of chest is the sound of: heart beat pulse heart contraction heart relaxation 2. Name the largest artery in the human body? aorta vena cava pulmonary artery arterioles 3. This is not an organ to serve as carrier for blood: lung arteries veins capillaries 4. What kind of blood is carried out through arteries? oxygenated and reddish oxygenated and bluish deoxygenated and reddish deoxygenated and bluish 5. Dr. Farhan suggested to treatment a patient that opens up narrowed blood vessels without surgery, using small balloons. What is the name of this treatment? angiography ECG open heart surgery angioplasty 6. What do you call the first root that arises from radicle of the seed? primary root secondary root tertiary root quaternary root 7. The area of young roots where most of the absorption takes place is: root epidermis root hair root cortex root vascular bundles 8. The key organ for transportation of water from roots to upper parts of plant is: root hair xylem phloem epidermis 9. How will you label the special openings that allow gaseous exchange in leaves? guard cell stomata mesophyll chloroplast 10. What feature is naturally adapted for the prevention of water loss in leaves? waxy cuticle hair epidermis stomata B. Answer the following questions briefly. 1. What is pericardium? What is its function? Ans: Pericardium is a double membraned protective covering around heart. It lubricates the heart and prevents it from injuries and hold the heart in accurate position. 2. Lungs work to purify blood. Justify the statement. 33 Teacher Resource Pack Guide Science 7 Ans: Lungs work to purify the blood as they enrich the blood with fresh oxygen that is inhaled by them and remove carbon dioxide from blood that is then exhaled out. 3. Differentiate between artery and vein. Ans: Difference between inhalation and exhalation is given below: No. Artery No. Vein i. Arteries are thick walled blood vessels. i. Veins are thin walled blood vessels. ii. Arteries carry oxygenated blood. ii. Veins carry deoxygenated blood. 4. Define transpiration. Ans: Transpiration is a process where plants absorb water through the roots and then give of water vapours through pores in their leaves. 5. How is food transported in plant? Ans: Food is transported in plants through phloem vessels. C. Answer these questions in detail. 1. Explain the transport system in humans. Ans: Transport system in humans: The process of moving materials into and out of the cells within an organism is called transport. Transport system in humans not only circulates the blood but also transports oxygen, carbon dioxide, nutrients and blood cells to the whole body. It consists of blood (RBCs, WBCs and platelets), heart, lungs, kidneys as well as lymphatic system. Lungs show a key role in the transport system as they purify the blood. The transport system provides food, prevent disease and stabilizes temperature and pH of the body. Transport system is known as circulatory system or the cardiovascular system in animals and humans and as the vascular system. 2. Describe the structure and function of heart and blood vessels. Ans: Circulatory system and its components: Human circulation system consists of heart and blood vessels to transport materials. The structure and function of these components are as follow: Structure of heart: The heart is a strong muscle present inside the left side of chest above the diaphragm. It is just of the size of a clenched human fist. Heart is made of cardiac muscles. The heart is placed within a fluid-filled cavity called the pericardial cavity and is enclosed by pericardium. It is a hard double membrane protective layer around the heart. This layer mainly lubricates the heart and holds it in accurate position. Heart is divided into four chambers: two auricles (the right atrium and left atrium) and two ventricles (right ventricle and left ventricle). The atria is the receiving chamber for the blood. It is linked to the veins for carrying blood to the heart. They (auricles) are smaller in size than ventricles. They possess thin muscular walls. The ventricles are large and stronger pumping chambers. Their task is to send the blood out of the heart. The ventricles are connected to the arteries that carry blood away from the heart. 34 Teacher Resource Pack Guide Science 7 The heart chambers are interconnected for blood transfer through special openings known as valve. The four valves present in human heart allow unidirectional flow of blood. These valves also determine the pathway of blood. Superior vena cava (a large vein) joins with several veinlets coming from upper parts of human body to provide blood to right atrium in heart. The inferior vena cava is the largest vein of body into which the veins from the lower trunk join to reach the right atrium of the heart. Function of heart: The heart performs the following functions: 1. It regulates the accurate supply of nutrients and oxygenated blood to all parts of the body. 2. The heart contains both the oxygenated and deoxygenated blood. It is its job to keep both of them separate in order to avoid contamination in the pure blood. Structure of blood vessels: There are three types of blood vessels that arise from heart. They carry blood to different parts of the body. These vessels are arteries, veins and capillaries: a. Arteries possess thick muscular walls. They can resist the high pressure of blood when it is pumped from heart. The biggest artery in human body is the aorta, which leaves the heart and divides into smaller arteries. b. The wall of the veins are thin because the blood flow is at a much lower pressure here. To prevent the back flow of this lower pressure of blood, the veins contain valves. c. Capillaries are microscopic, thin-walled vessels that connect arteries to veins. Function of blood vessels: The functions of blood vessels are as follow: a. Arteries provide oxygenated blood from the heart to the rest of the body. b. Veins bring deoxygenated blood back to the heart through the inferior and superior vena cava, which lead to the right atrium. c. Capillaries take blood through the organs and tissues. 3. Highlight the working of the circulatory system. Ans: Working of the circulatory system: In humans, oxygenated blood (present in left atrium and ventricle) appears reddish in colour whereas, deoxygenated blood (present in right atrium and ventricle) appears bluish in colour. The blood (carrying digested food) absorbs oxygen from lungs. After oxygenation, this oxygenated blood (along with digested food) comes to the left atrium of heart from the lungs in the pulmonary vein. Bicuspid valve of heart sent this oxygenated blood to left ventricle. On contraction, the heart pumps this blood forcefully to the aorta. Aorta provides it to the whole body through network of arteries and capillaries. The food and oxygen present in this blood is also transported to cells and tissues. At the same time, the carbon dioxide and nitrogenous waste are released into the blood from the cells. Blood takes back this deoxygenated blood (with carbon dioxide and nitrogenous waste) through veins to kidneys. Kidneys remove all nitrogenous waste from the blood. Then through vena cava, it returns to the right atrium of heart from the kidney. The heart pumps the deoxygenated blood to the lungs through pulmonary arteries. The pulmonary artery has 35 Teacher Resource Pack Guide Science 7 semilunar valve that prevents the back flow of blood. Blood pressure is usually high when it moves away from heart; it is usually low when blood moves towards the heart. 4. Identify scientific developments that provide alternatives for dysfunctional body parts. Ans: Scientific developments as alternatives for dysfunctional body parts: At times, the organs of circulatory system (heart, blood vessels, lungs and kidney) may become dysfunctional. Various scientific developments have been made by scientists during recent years to alternate the dysfunctional parts of the human body. For example, if the heart becomes dysfunctional, doctors investigate the condition of the heart internally through electrocardiogram (ECG). Angiography and angioplasty: Heart attack is a heart disease that is caused due to severe blockage of blood artery due to deposition of cholesterol. The condition is examined by angiography. The technique is an X-ray examination of these arteries. To fix these bad conditions, angioplasty is adopted. It is a procedure that opens up narrowed blood vessels without surgery, using small balloons (stent). Artificial valves: If any of the four valves stops working, scientists have developed artificial valves to replace them. This is done through open-heart surgery. Bypass surgery: Whenever the arteries inside heart become dysfunctional, bypass surgery is done to cure this condition. It is a surgical procedure to restore the normal blood flow in a blocked coronary artery. It is also known as coronary artery bypass surgery. Heart transplantation: A heart transplant is a surgical procedure that is performed on patients with end-stage heart failure. The patient's own dysfunctional heart is removed and is replaced with the donor’s heart. Artificial heart: Artificial heart is a device developed by scientists that replaces the natural heart. Sometimes, it is almost impossible to process natural transplantation of heart, in that case, artificial heart is used. Artificial pacemaker: Pacemaker is present inside right atrium to check heart beat rhythms. Sometimes, this natural pacemaker becomes dysfunctional. An artificial pacemaker is an alternate medical device designed by scientists which can regulate the beating of the heart. 5. Find out that some disorders in human transport system can be affected by diet. Ans: Disorders in circulatory system due to diet: The foods with large quantities of saturated fats (cholesterol) have negative impact on health. The heart is a muscle, and like other body muscles, it depends upon a balanced supply of blood. If vessels become hard due to deposition of cholesterol, they are more susceptible to tear. This can lead to clot formation and clogging of the vessels. Clogging of the arteries that feed the heart leads to many disorders such as high blood pressure and even to heart attack. High blood pressure: Due to clogged arteries, blood flow becomes difficult leading to high blood pressure. The condition if prolonged can lead to heart attack. Anemia is the condition 36 Teacher Resource Pack Guide Science 7 when our heart lacks the oxygen in the blood. It happens when our diet lack iron. This can be so severe that it may lead to heart failure or the heart becomes enlarged. Diabetics: A diabetic patient possess high glucose level in the blood that damages the blood vessels. Diabetic patients are more prone to heart diseases. 6. Elaborate the absorption of water in plants through roots. Ans: Transport system in plants: Transport system in plants serves to transport water, food and minerals throughout the plant. Here is the process of transportation. Absorption of water in plants through roots: Higher plants have roots penetrated in soil. Food produced in leaves needs water and prepared food is needed by rest of the parts. So, there is a proper need to carry out transportation in higher plants. They absorb water through the entire surfaceroots, stems and leaves. But, the water is absorbed by roots mainly. Primary, secondary and tertiary roots are combined to make a root system of plants. The area where most of the absorption takes place is the root hair of young roots. The root hairs are tiny structures. They take in water from the intervening spaces mainly by diffusion. The absorbed water passes through cell membrane and reaches the vacuole inside the epidermal cells. As the root hairs are extremely thin and large in number, they provide enormous surface area. Water inside the vacuole of root cell is then pushed into xylem vessels. Xylem is the key organ for transportation of water from roots to upper parts of plant. Xylem in roots provides water to upper stem and then water is shifted to branches of leaves. In this way, water is transported to whole plant. Transportation of water along with minerals is conducted for various purposes: 37 Teacher Resource Pack Guide Science 7 1. Water acts as a reactant during the process of photosynthesis. 2. It sustains the rigidity in cells of roots, leaves and stems. 3. It lowers down the temperature of leaves through the process of evaporation. 4. It provides essential nutrients and minerals throughout the body. 7. How do the structures of the roots, stem and leaves of a plant permit the movement of food, water and gases? Ans: Plants need food and water to live. Water is absorbed through roots and food is prepared in leaves which are aided by exchange of gases. In order to transport water (from roots) and food (from leaves) to the whole plant equally, there are two structures i.e. xylem and phloem. These structures are elongated tubes that interlink each part of the plant, just like the net of blood vessels spreads through out the body in animals. Plants transport water through xylem. The process is known as transpiration. Food is transported through phloem and is known as translocation. Roots: Thousands of tiny root hair is present on each root. Water and minerals from the soil are absorbed into the root hair by process of diffusion. “Diffusion is the movement of a substance from where it is in large amount to where it is in small amount”. As the level of water in roots increases, a pressure is created in the root cells. This pressure pushes water and minerals to the upper parts of the plant. Stem: Water vapours evaporate from the leaf and create a kind of suction in stem. This creates a transpirational stream that pulls water up from the root. Mature xylem cells act like open-ended tubes to allow free movement of water through them. Roots also produce the root pressure that forces water up through xylem vessels. So, stem is basically designed to promote flow of water from roots to leaves. Stem also provides prepared food from leaves to lower parts of the plant through phloem. Leaves: In a leaf, three types of material movement i.e. water, food, gases take place. Food and water exchange takes place through phloem and xylem respectively. Whereas, for the exchange of gases specialized structures are present. As, a leaf needs carbon dioxide to prepare the glucose (food) and oxygen, therefore, there is need to promote gaseous exchange in leaves. For this purpose, they contain openings, called stomata. They allow gaseous exchange in the epidermis of leaf. On each side of the stoma, there is a guard cell. These cells check the excessive gaseous exchange by their customized opening and closing. Gaseous exchange also takes place inside the leaf. The specialized cell inside the leaf i.e. mesophyll cell in a absorb gases. These gases are present in the air spaces between the spongy mesophyll and palisade mesophyll cells. Sometimes, due to high temperature, rate of transpiration is high leading to great water loss from leaf surface. For the prevention of this water loss, leaf is coated by a waxy cuticle. Moreover, leaves are adapted to have lesser number of stomata at their upper surface. This helps them to reduce water loss. 38 Teacher Resource Pack Guide Science 7 Unit # 3 REPRODUCTION IN PLANTS Lesson 1 Topic: (3.1: Pollination) Teaching objectives: ⦁ Explain the process and need of pollination. ⦁ Explain different types of pollination. Key vocabulary: Genetic information, seeds, pollination, fertilization, sexual reproduction, anther, stigma. Materials required: ⦁ Board (White/Black), marker/chalk, CSS – Science book – 7, Fresh hermaphrodite flower (rose, motia, etc.) Introduction: Ask students some questions that may refresh their previous knowledge about the lesson i.e. parts of flower, pollen grains, seeds. The teacher may use the following questions as well: Can you name parts of flowers? (Ans: Sepals, petal, carpel, ovary) Which of the following parts of flower participate in reproduction? (Ans: Stamen, Carpel) What is seed? (A reproductive structure) How does a seed form? (Ans: By fertilization) Do you know about pollens? In which part of flower, pollen produce? (Ans: Carpel) In which part of flower a seed is produced? (Ans: Ovary) In spring season, you might have listen some people have pollen allergy. What do you know about it? After having answers from students, explain them a little the answers of these question. Then introduce the today’s topic. Tell them that in plants seeds transfer the characteristics of one generation to other. In order to produce seeds, two important stages participate. One stage is the transference of pollen grain in female reproductive part and the other stage is fusion of pollen with egg. The former stage is called pollination and later one is called fertilization. Today we are going to investigate first stage i.e. pollination and study its types. Development: Show the floral structure to class. It would be better to use models of flower. Activity: It would be a good activity if the teacher provide fresh flowers to each student or to pairs of student (as per capacity). Ask students to identify their parts and note them in their note books. Help them if they find difficulty to identify parts. Then separate out stamen and ask students to do the same. While dealing with stamens. Students may feel the presence of some small particles on their hands. Ask students to guess it. If students could not tell them it is pollen. Explain about pollens. Show them its picture. Tell them that pollen is the male reproductive structure in plants. When this pollen fuse with egg in ovary (female reproductive organ), seed is formed. When students have separated stamen, ask them to separate pollens from carpel by using a thin pointed article. The may use camel hair brush or safety pins etc. Then ask them to observe pollen under dissecting microscope. Help them to do so. Ask them to separate out female reproductive part i.e. ovary. Help students to identify and separate ovary. Ask students to vertically dissect the ovary (make a T.S of ovary) and observe it under microscope. Now, explain the lesson. Tell students, when pollen from carpel reaches the stigma of ovary, it is called pollination. 39 Teacher Resource Pack Guide Science 7 Ask students to write the definition of pollination. Write on board the types of pollination i.e. self-pollination and cross pollination. Ask students to place stamen and ovary on their copy side by side at some distance. Draw an arrow from stamen to carpel and label it as self-pollination. Then separate out ovary from other flower. (The flower species should be same). Place the other flower’s ovary beside stamen of first flower and draw a carved arrow from stamen to ovary of other flower. It is called cross pollination. When students have understood the concept of self and cross pollination, ask them to explore the advantages of each type. Divide class in two groups, one is to study self-pollination and other is to study cross pollination. Ask them to consult CSS Science book for class 7 and prepare their topics. Then, call some students from group – 1 in front of class and ask them to explain their points. It would be their assessment. The teacher should note down the key points on board as well. Similarly: Call the other group to present their topic. then explain the topic by yourself. Closure: Revise all the main points from board i.e. Transference of pollen from anther to stigma is called pollination. If pollen transfers from anther to stigma of same flower, it is called self-pollination. If pollen transfers from anther to stigma of the other flower but of same species, it is called cross pollination. Self-pollination is fast and quick with identical genetic information while cross pollination is time taken and cause varieties in new generations. Home work: Assign the following questions as homework. Define pollination. Describe the peculiar features and importance of self-pollination and cross pollination. Tell students about the next day topic i.e. Factors involved in cross pollination. Lesson 2 Topic: (4.2: Factors involved in cross pollination) (4.3: Cross pollinated plants) Teaching objectives: ⦁ Explain students that flowers are adapted to attract specific pollinators. ⦁ Explain that many plants depend upon animals for pollination and many pollinators depend upon plants for food. Key vocabulary: Pollinators. Materials required: ⦁ Board (white/black), marker/chalk, CSS – Science book for Class – 7, fresh flowers. Introduction: Hold up flowers and ask students to identify the process by which flower reproduce. Define the term pollination and ask students to describe what they know about pollination. Ask students what they think how does a pollen transfers from one flower to another in cross pollination. Let students think for some time. Most probably students would answer rightly. If majority of students fail to answer correctly, ask some other questions e.g. What do you think, why do insects come to flowers? What happens when an insect lands on a flower? (Expected answer: Pollen grains may stick to them). Write students responses on board. Explain them little the answers of these questions. Ask students draw a T-chart in their note books as follow. Biotic Factors Abiotic factors 40 Teacher Resource Pack Guide Science 7 Ask them to think which biotic and abiotic factors may be carrier for pollens. Complete the table by students responses as follow. Biotic Factors Abiotic factors Insects Wind Birds, Animals Water Then ask students to name some insects that may carry pollen with them. (Expected answer: bees, flies, hoppers, etc.) Name some other insects that may be used are carrier. Divide the class in four groups. Assign each factor to prepare for presentation i.e. animals as pollinators, insects, water and wind. Make a list of important points required by students to prepare. How/Why does the particular factor/ agent interact with flower? Name some members of that particular factor. How do they transfer pollen? Any special character / feature about that factor. Give some time to prepare. Ask students they may consult CSS science for Class 7. While they are preparing, the teacher would roam about the class and discuss with each group its specific topic. Make a table on board and ask students to copy it. (The complete table is given below) Call one group to present their topic. The teacher would ensure and encourage that each student participate. The students would present according to question list previously written. Then complete the table by students responses. Such as, one has been done for you. Animals Insects (To be filled by teacher) Come to plants for food i.e. leaves, branches, nectar Biotic Monkeys, birds, humans Pollen grains stick with their body. Then are dropped when these animals reach to other flowers. Wind Water (To be filled by teacher) Wind pollinated plants produce pollen in large quantities. Wind/air is present everywhere. The pollens that are liger in Abiotic weight are transported by wind. Most conifers and crops are wind pollinated. e.g. pine, spruce, firs, nuts, e.g. Ask students to name some plants that are cross pollinated. Closure: Revise all the main points from board. Read the lesson from CSS – Science book – 7 with correct pronunciation. Homework: Assign the following questions as home work. Describe some factors that may affect cross pollination. Test Exercise – 1 A. 1. 2. Choose the correct answer and fill the circle. What is the first step of sexual reproduction in plants? pollination fertilization seed formation flower production The process that helps in development of new species of plants is: 41 Teacher Resource Pack Guide self-pollination Science 7 cross pollination fertilization budding 3. Choose the example of wind pollinated flower: water hyacinth pine hydra eel-grass 4. Which of the following pollens are produced in wind-pollinated plants? light and dry pollen heavy and dry pollen light and wet pollen heavy and wet pollen 5. The plant that can cross-pollinate with other species of its family is: carrot radish spinach cauliflower B. Answer the following questions briefly. 1. Define pollination. Ans: Pollination is defined as the transference of pollen grains from anther to stigma of a flower. 2. Differentiate between self-pollination and cross pollination. Ans: Difference between self-pollination and cross pollination is as follows: No. Self-Pollination No. Cross-Pollination i. The type of pollination in which pollen i. The type of pollination in which pollen grains from anther fall on stigma of same grain from anther of one flower fall on the flower. stigma of another flower of same species. 3. There are several types of pollinating agents. Name them. Ans: There are several types of pollinating agents. These are Insects: Moth, butterflies, bees, flies. Birds: Animals, wind and water. 4. Insects help in pollination. Justify the statement. Ans: Insects help in pollination. When an insect pollinator visits the flower to collect nectar, it accidently picks up the pollen on its body. As it goes to other flowers, pollen transfers to other flower. 5. Name some cross-pollinated plants. Ans: Plants which are cross-pollinated include grasses, alfalfa, banana, maize, catkins, dandelions, maple trees etc. A large number of crops that can cross-pollinate are squash, pumpkins, cucumber, melon, broccoli, summer radishes, tomato, beans, beets, carrot, cabbage, cauliflower, corn, onion, pea, pepper, spinach, turnip, water melon etc. Lesson 3 Topic: (3.4: Sexual and asexual reproduction 1st half) Teaching objectives: ⦁ Define the term asexual reproduction. ⦁ Describe several forms of asexual reproduction in plants. Key vocabulary: asexual reproduction, gametes, fusion, vegetative, propagation, cutting, layering, fragmentation, spore formation. Materials required: ⦁ Board (White/Black), marker/chalk, CSS – Science Class – 7, small potatoes, several cuttings of succulents or other plants that will root in water, live planarian, distilled water, rulers, dropper, razor blades, hand lenses, hard-boiled egg yolk, permanent marker. Small stems of roses sowed in small pots. Preparation by teacher: At least 2 weeks ahead of time (more if you want to get some good root growth on your potatoes), purchase some small potatoes and some succulents. Place the potatoes in a paper bag and leave them in a cupboard. Cut some stems off from your succulents and place them in a glass of water. Refill the water as it evaporates. 1. In the same way do with jasmine plant. Cut one branch of rose stem and tie it with another stem. Sow it into soil and water’ it daily. 42 Teacher Resource Pack Guide Science 7 In a few days' time, your potatoes and succulents should begin sprouting roots. Before the lesson, place them in beakers or clear cups so your students can observe them. Warm up: Begin the lesson by asking students if they have ever found a forgotten potato in the back of their cupboard. What happened to the potato? (Alternatively, ask them what part of the plant they are eating when they eat carrots or potatoes. What would happen if they were to put one into the ground?) Pass around your rooted potatoes and succulents. Explain to students that they are witnessing examples of asexual reproduction, or cloning, in plants. They will be learning more about asexual reproduction in today's lesson. Introduction: Ask some questions that may lead students towards today’s lesson e.g. What is meant by the term reproduction? Can plant develop a new plant if only one parent is there? Algae do not have flowers, how do they develop new plants? Do all plants produce seeds? Write students responses on board. Then introduce the today’s topic. Tell students today they will learn how plants develop into new plants when there is no seed formation. Development: Explain them about asexual reproduction. Points to be explained: The lower plants that do not develop flowers, do not produce seeds and grow through asexually. In such plants male and female parents do not participate. The off springs of such plants are exactly identical to parents. There are no variations in next generations. Greater number of off springs is produced because it is a rapid process and every part of the parent plant may develop into new plants. Just like seed formation, no wait is there. Asexual reproduction mainly occur in lower plants but some higher plants e.g. rose, potatoes, etc. may also grow through asexually. There are many modes/way to grow by asexually e.g. vegetative propagation, cutting, layering, fragmentation, spore formation. After explaining the introduction to asexual reproduction, divide class into five groups. Assign one mode of asexual reproduction to one group. Explain them each group will prepare its assigned mode and will share its mode with whole class. Ask them to read/consult CSS-Science book-7. Encourage students to underline and take notes while they read. Once students have finished reading and taking notes, ask the group one i.e. vegetative propagation to stand up and share its information. The most expected response or understanding would be: → The mode of reproduction in which new plants develop from roots, leaves, stem, buds etc. → The plants that grow by vegetative reproduction is potato. When students have done, show your rooted potatoes. Explain to students, they are observing vegetative reproduction. As potato is tuberous stem it grows into new plant. Explain them the procedure that you did previously to grow potatoes. Next call the second group named “cutting”. Ask to explain its topic. The most probable explanation might be as: → The type of reproduction, in which stem of a growing plant is cut and is sowed into soil. After some days it grows to new plant. → Roses are grown through cutting. When students have done, show them the potted rose stem, you have prepared previously. Explain them how did you cut the stem of rose and sowed. As the teacher has done it a week before, so, new leaves would have begun to arise. 43 Teacher Resource Pack Guide Science 7 Then call the third group that has studied layering. The most probable explanation of layering would be as: → When the stem of a plant e.g. Jasmine sowed into soil without separating it from the plant, it grows in to new plant, develops leaves and branches. Jasmine stem is week so bends down easily. Then the stem of new developing plant is sown that grows into new plant and the process goes on. → When students have done with it, show them your previously prepared, grown jasmine plant. Explain them how did you grow it. Bring out the stem of Jasmine from soil, it have new developing buds and show them to students. In the same way, explain the other two types of asexual reproduction. Closure: Draw a table on board with five columns each named as a mode of reproduction. The table should have two rows as follow: Mode Feature Vegetative Cutting Layering Fragmentation Spore formation propagation Difference Example Complete the table by student’s responses. Home work: Assign the following questions as homework. What do you know about a sexual reproduction? How many types of asexual reproduction are there? Write brief note on each type. At the end of the lesson tell students, they have learned how do plants grow without seed and the next day they will learn what happen when pollen grain reaches on the stigma and how does seed from. Lesson 4 (3.4: Sexual and asexual reproduction 2nd half; sexual reproduction) (3.5: Fertilization) (3.6: Seed and fruit formation) Teaching objectives: Make students able to ⦁ Define the term sexual reproduction. ⦁ Explain what happens when pollen falls on stigma. ⦁ Explain the formation of seed and fruits. ⦁ Compare sexual and asexual reproduction. Key vocabulary: Sex cells, fertilization, pollen tube, stigma, style, ovary, zygote, seed coat, inheritance. Materials required: ⦁ Board (White/Black), marker/chalk, CSS – Science Class – 7, chart/models of carpel showing stigma, style, ovary and seed. Introduction: Recap the previous lesson by asking different questions e.g. Can you name some plant that possess flowers but do not reproduce through seeds? How is cutting mode of reproduction different from vegetative propagation? After having responses from students, introduce the today’s topic. Tell them that they are going to study a new type of reproduction in which both parents (male and female) participate. In such type of reproduction, absence of one parent ceases the process of development. Such type of reproduction is called sexual reproduction. In sexual reproduction, male parent donate pollen grains and female parent provide egg and place for fertilization. It might possible that both male and female organs are present on single flower. Such flowers are called hermaphrodites. Activity: Ask students to draw the structures of stamen (anther and filament) and carpel (stigma, style and ovary) on their note books. Label both structures. Then show the transference of pollen grain from anther to stigma. The teacher should draw the structures on board and explain step by step. Next, draw a pollen tube from stigma to ovary. Explain that when pollen reaches the stigma, a pollen tube develops and reaches the ovary, where egg is present. Pollen fuses with egg. This process is called fertilization. Topic: 44 Teacher Resource Pack Guide Science 7 Draw pollen tube and show the pollen grain travelling through it. Then while explaining fertilization, show pollen grain in the ovary joining the egg. Next, explain what happens when fertilization have been taken place. Sepals and plants fall off, ovule develops into seed. An embryo also forms that grows into zygote. The zygote grows by cell division and forms fruits. After this, give students some time to study the differences between sexual and asexual reproduction. Then draw a T-chart on board. Ask student to compare both type of reproductions. Complete the chart by students’ participation. It would be their assessment. Asexual Reproduction Sexual Reproduction Only one parent plant is involved. Both male and female parents are involved. Occurs in lower plants. Occurs in higher plants. Reproductive organs may not present. Fully developed reproductive parts are present. Fertilization does not take place. Fertilization give rises to zygote. Characteristics of only one parent are inherited. Characteristics of both parents are inherited. No need of seeds. Seeds are used to get new plants. Homework: Assign the following questions as homework. 1. Compare the sexual and asexual reproduction. 2. How is a seed form? 3. Explain the process of fertilization. Test Exercise – 2 A. 1. Choose the correct answer and fill the circle. Sara wants to label the female part of flower. What term will she use? 45 Teacher Resource Pack Guide sepal Science 7 petal stamen carpel 2. We can observe the process of layering in: rose tulip jasmine bryophyllum 3. Into which condition ovary turns into after fertilization? flower fruit seed leaves 4. Pollen grains are produced in: stamen carpel filament ovary 5. Following plants show spore formation except: algae fungi mosses water lily B. Answer the following questions briefly. 1. What is the role of stamen in reproduction? Ans: Stamen produces pollen that fuse with egg in the ovary and forms seeds. The seed then develops into new plant. Thus, without stamens fertilization would not be possible as pollen would not be available. 2. Asexual reproduction yields no variation among organisms. Justify the statement. Ans: Asexual reproduction does not yield variation among organisms because it does not involve gametes of two parents. As single plant is involved in reproduction, that eliminate the chances of variations. 3. How does the process of vegetative propagation occur? Ans: Vegetative propagation is a type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds. Plants such as potatoes grow by this method. 4. Enlist any two differences between asexual and sexual reproduction. Ans: Difference between sexual and asexual reproduction is as follows: No. Asexual Reproduction No. Sexual Reproduction i. Single parent involves. i. Both male and female parents are involved. ii. No genetical variations. ii. Genetic variations take place among next generation. 5. Fertilization leads to seed formation. Do you agree? Ans: Yes, fertilization leads to seed formation. In fertilization, pollen and egg fuse and gradually develop into seeds. Review Exercise A. 1. 2. 3. 4. 5. 6. 7. Choose the correct answer and fill the circle: What is the colourful part of flower? petals sepals stamen carpel Which of the following is the example of budding? cactus jasmine rose tulip The initial step in the process of sexual reproduction in plants is: pollination fertilization seed formation fruit formation Which of the following is not an example of cross-pollinated plants? cucumber melon sunflower radish Which of the following is not an insect pollinator? bat honey bee fly wasp Which of the following plant shows cutting? rose moss algae fungi Upper part of the ovary is: 46 Teacher Resource Pack Guide anther 8. Science 7 stigma style filament Which is the result of fertilization of ovules? seed fruit flower leaf 9. What is the pollinating agent in Hydra? animal insect wind water 10. Formation of zygote happens in: anther stigma filament ovary B. Answer the following questions briefly. 1. What is the function of flower in sexual reproduction? Ans: Flower is a reproductive organ. It produces seeds that develop into new plant. 2. Pollination is the essential step in sexual reproduction. How? Ans: Pollination is an essential step in sexual reproduction as this process is responsible to provide pollen to the ovary for fertilization. In the absence of pollen, fertilization would not happen. 3. Differentiate between stamen and carpel. Ans: Difference between stamen and carpel is given below: No. Stamen No. Carpel i. Stamen is male reproductive part of a flower. i. Carpel is female reproductive part of a flower. ii. Stamen produces pollen. ii. Carpel produces egg. 4. Define fertilization. Ans: Fertilization is defined as a process of fusion of pollen and egg leading to the formation of seed. 5. How are fruits and seeds formed? Ans: After fertilization, ovary develops into fruit and ovules develop into seeds. C. Answer these questions in detail. 1. Compare self and cross-pollinations in plants. Ans: Pollination: All flowering plants depend on pollination for the reproduction. Pollination is the first step in the process of sexual reproduction in plants. “Pollination happens when a pollen grain is transferred from an anther (male part of a flower) to stigma (female part of a flower)”. Pollination can only be successful if the flowers are from the same species. For example, pollen from tulip plant can only pollinate with another tulip plant. There will be no successful pollination (fertilization) if the pollen from rose plant reaches the flower of tulip. Types of pollination: There are variations in the mode of pollination in plants. These modes are of two types. Self-pollination and cross-pollination. Self-pollination: This type of pollination occurs when pollen grains from the anther fall directly on the stigma of the same flower. It is the basic type of pollination as it only involves one flower. This type of pollination is simple and quick. It results in identical transfer of genetic information. Cross-pollination: This type of pollination occurs when pollen grains from the anther of one flower fall on the stigma of a different flower of same plant. It is the complex type of pollination as it involves different flowers (belonging to same species). It results in an increase in genetic information to create unique off springs. 2. Describe various factors involved in cross-pollination. Ans: Factors involved in cross-pollination: Transference of pollen from one flower to another in cross-pollination becomes possible by different pollinating agents (also known as pollinators) such as birds, bees, bats, butterflies, moths, beetles or other animals. Some abiotic factors such as wind and water also drive the pollination process. Animals as pollinator: The plant uses its colourful flowers to attract an animal pollinator. Vertebrates can be important as pollinators. The most prominent are birds and bats. But 47 Teacher Resource Pack Guide Science 7 pollination by monkeys, lizards and rodents has also been recorded. Among the pollinating birds are humming birds, honey-eaters and sun-birds. Humans can also act as pollinators like gardeners. Pollen grains stick to their bodies and drop when they move to other flower. Insects as pollinator: Insect pollinators include bees, honey bees, bumble bees, wasps, ants, flies bee flies, hover flies, mosquitoes, butterflies, moths and flower beetles. When the insect pollinator visits the flower to collect nectar, it accidentally picks up the pollen on its body. As it goes on to other flowers, an effective pollinator will deliver some of that pollen to the female part of the flower of the same plant species. Wind as pollinator: Many pollens are transported by wind. Most conifers and about 12% of the world's flowering plants are wind-pollinated. World's most important crop plants (wheat, rice, corn, rye, barley and oats) are also wind-pollinated. Many economically important trees are also wind-pollinated. These include pines, spruces, firs and nuts producing trees. Wind-pollinated plants produce larger quantities of light weight, dry pollens in their small flowers that can be carried easily through the wind. Water as pollinator: Pollen grains can also float on the water's surface until it contacts the flowers of same species. This is relatively rare. This water-aided pollination occurs in water weeds and water hyacinth, water lettuce, hydrilla and in eel-grass. In a very few cases, pollen travels underwater. 3. Differentiate between sexual and asexual reproduction. Ans: Following is the comparative analysis between asexual and sexual mode of reproduction: Asexual Reproduction Sexual Reproduction Only one parent plant is involved. Both male and female parents are involved. Occurs in lower plants. Occurs in higher plants. Reproductive organs are not present. Fully developed reproductive parts are present. Fertilization does not take place. Fertilization give rises to zygote. Characteristics of only one parent is inherited. Characteristics of both parents are inherited. No need of seeds. Seeds are used to get new plants. 4. Explain the process of fertilization. Ans: Fertilization: Fertilization is the next step to pollination. Once the pollen grain lands on stigma, it creates a pollen tube through the style which enters into the ovary (stalk connecting the stigma and ovary). Once the pollen tube is formed, the pollen grain send its sperm cells to the ovary through the tube. When the sperm cells reach the ovary (place where egg cells are already formed), it combines with the egg to form embryo, and hence, fertilization occurs. 5. Describe seed and fruit formation. Ans: Seed and fruit formation: After fertilization, many changes take place in flowers. The ovary grows into a fruit (ripened ovary) and other parts of the flower (sepals, petals, and stamen) fall off. The ovule develops into seed. Once the embryo is formed, the cells of the embryo will start to grow in a normal method. After the embryo grows beyond its two celled stage, it is called zygote. As the zygote starts to grow, ovary wall begin developing into fruit and oval will grow to form seed. The seed contains an embryo enclosed in a protective seed coat. The seed will free to be released from the parent plant. It will be able to grow into a new plant and hence continue the reproductive cycle again. 48 Teacher Resource Pack Guide Science 7 Unit # 4 ENVIRONMENT AND FEEDING RELATIONSHIP Lesson 1 Topic: (4.1: Ecosystem) (2.2: Components of ecosystem) Teaching objectives: ⦁ Explain the ecosystem and habitat. ⦁ Describe the components ecosystem and their relative importance. Key vocabulary: Ecosystem, population, ecology, producers, consumers, decmposers. Materials required: ⦁ Board (White/Black), marker/chalk, CSS – Science book for Class – 7, charts showing producers, decomposers and consumers. Introduction: Ask some questions to explore the students previous knowledge, as at this stage students have strong base for environment and its components e.g. How would you define environment? What things make our environment? Is there any difference between desert environment and cold region environment? What thing / factor differentiate the both environments? Can the both environments be similar? If Yes, how? What is the prime source of food in a desert environment? Write students responses on board and tell them they are going to study about environment and its component today. Development: Then explain the term environment, the teacher can use the pictures of different environments e.g. desert environment, mountainous environment, land and marine environment. Activity: Ask students to separate out biotic and abiotic components of each environment and write in the notebooks. Meanwhile, the teacher would draw a chart as follow: Desert Marine Land Environment Mountain environment Environment environment Biotic component Abiotic component Then ask students to share their findings. Write the correct response on the board and complete the table. Desert Marine Land Environment Mountain 49 Teacher Resource Pack Guide Science 7 environment Environment environment Cactus, lizard, Whale, fish, algae, Trees, small plants, Markhor, Conifers, Biotic weeds, herbs, mosses, ferns, component snake, Rats, herbs, corals Tortoise, few humans eagle, snakes, octopus etc. animals, humans fungi, goats, bacteria, virus fungi bacteria, virus fungi birds, bacteria virus bacteria, virus fungi fungi Water, dim light, Soil, light, Snow, mountains, Abiotic Sand, high cozy temperature, temperature, water soil, low component temperature, dry climate, intense rocks, shells temperature, light light, water scarcity Appreciate students’ efforts and for having strong concept for biotic and abiotic components. Tell students, both abiotic and biotic components are necessary for survival in a particular habitat. Activity – 2: Now ask students make a list of animal’s representative of each environment. The teacher should draw this list on boards and complete it by students’ responses as follows: Desert environment Marine Land Environment Mountain Environment environment Markhor, Donkeys Desert mouse Fish Horse, cat, dog, lion, elephant etc. Camels Octopus Lizards Jelly fish Snake Star fish Note: The teacher may include any other animal for particular environment as per student’s responses. Then, explain the terms ‘population’ and ‘habitat’. Tell students, that some kind of animals / plants that live in a particular environment are called population of that environment. e.g. camel population, fish population. And the environment where a particular species live is called its habitat. e.g. desert is habitat for camels. Camels can’t live in marine or mountainous environment. Now ask students to write the definitions of population, habitat, biotic components, abiotic components. Help students in their task. Ask questions to students: Where do animals get their food from? (Answer: from plants) What would happen if all plant destroys? (Ans. There would be no food for animals). After having answers from students, explain them producers, consumers and decomposers. e.g. The living beings that prepare their own food are called producers. Therefore all plants are called producers. (Explain it further) Animals can’t prepare their food. They depend upon plants directly or indirectly by eating other animals. So, animals are called consumers. (Explain it as per curriculum) When animals and plants die, their dead bodies contain nutrients. It is necessary to return these nutrients back to environment. This job is done by decomposers. They break down the dead animals and plants into simpler ones. Bacteria and fungi perform this task. Activity – 3: Ask students to go back to the table prepared during activity – 1. Ask students to pick out producers, consumers and decomposers from table – 1. Also write 3 characters in each category. They can include extra examples as well. Help students if they find any difficulty. Producers Consumers Decomposers Conifers Animals Bacteria Cactus Birds Fungi Pines Insects Herbs Weed 50 Teacher Resource Pack Guide Science 7 Closure: Revise all the main points from board. Read lesson from CSS Science book with correct pronunciation. Explain the terms if any. Homework: Assign the following questions as homework. 1. What are abiotic and biotic components of an environment? 2. Differentiate between producers, consumers and decomposers. Lesson 2 + 3 Topic: (4.2: Habitats) (4.3: Kinds of Habitats) Teaching objectives: ⦁ Explain that Earth supports many different animal habitats, each of which has distinct features and distinct animal population. Key vocabulary: Habitat, ecosystem, fresh water, sea, tundra, grass land, deciduous forests, coniferous forests, rain forests, arctic tundra, alpine tundra, tropical grass land, temperate grassland. Materials required: ⦁ Board (White/Black), Chalk/Marker, CSS – Science book for Class – 7, Chart of different habitats as per CSS – Science book, display pictures of each habitat for students. Introduction: Introduce the todays’ lesson. Tell students they are going to investigate home of different animals and plants. The teacher may ask some questions that may guide students for todays topic. What is a habitat? Why does habitat of camel is different from that of lion? What things make a habitat different from the rest? Can you name some habitats? Development: Explain the topic briefly. Explain them that different habitats are necessary for different animals. If all the habitats would same, there would be colossal race and competition for limited resources. Different habitats avoid this natural competition of food and shelter in an ecosystem. Explain that different animals only survive in their particular habitat because their bodies are adapted for conditions of that habitat. e.g. fish need water, Shark, needs saltish water, lion lives in forests. Activity: Divide the class into 6 groups. Tell students, they are going to research different habitats of the world. Each group will prepare a report on its habitat, that would include the following information: a) Physical description of habitat: Examples of habitat. Geographical location of habitat. Examples of animals and plants living in a particular habitat. On the board, write the names of different habitats students will investigate. 1. Forest habitat: Deciduous forests Coniferous forests Rain forests 2. Desert habitat: Hot and dry desert Cold desert 3. Aquatic habitat: Fresh water habitat Sea habitat 4. Gross land habitat: Temperate grasslands Moderate grass lane 5. Tundra habitat: Alpine tundra Arctic tundra Tell students as each habitat is further divided into its forms so, each group should make further groups among itself that deal with each sub type. It will make their task easy. Ask students to consult CSS – Science book for Class – 7 to prepare their topic. While students are preparing for their task, the teacher would roam about the class and discuss group the specific habitat of each group. It would be better to generally and briefly explain the habitat to the group. (The teacher can briefly explain the topic before starting the activity as well. Forest habitat: Tell them which type of habitats is called forest habitats. A habitat with abundant trees, plants and animals on a large area is called forests. Deciduous forests: The term deciduous means falling off at maturity or tending to fall off. These are the forests where trees seasonally shed their leaves, usually in autumn. These trees 51 Teacher Resource Pack Guide Science 7 shed of petals after flowering and shed ripe fruits. The climate in such forests is cool. During winter months water is generally not available to keep the leaves of plants alive. Coniferous forests: Trees in coniferous forests have needle like leaves and develop cones. These are evergreen forests. The climate in such forest is extreme cold. Therefore needle like leaves help to reduce water loss. Rain forests are found in regions lying on or near equator. They have lush green trees due to abundant rain fall. Desert habitat: It is the driest area due to the hottest climate. Fresh water is the water that has lesser amount of salts dissolved in it. So, the species found here could not survive in sea water that has higher salt concentration. Grassland habitats do not possess large trees. They have long grasses and small plants. These habitats are found on equator of earth. On the basis of climatic conditions, grassland habitats are of two different types’ i.e. temperate grasslands and tropical grasslands. Tundra is habitat where tree growth is hindered due to low temperature and short growing season. These habitats are tree-less mountainous tract. That is why, vegetation; here are dwarf shrubs, grasses and mosses. When students have prepared their topics, ask the group – 1 to present their topic. Note the key points on boards and ask students to note down as well. Then explain the topic by yourself. Show the pictures of that particular habitat. Make two lists of animals and plants found in each habitat. Ask students to copy it on their note books. In the same way, call all the groups and repeat the procedure as above. Ask students to pay attention to the animals and plants and try to relate them with environmental conditions of that habitat. When all the groups have done, revise the main points from board. Read the lesson from book with correct pronunciation. Tell students today they have learned about different habitats and the next day they will learn about the adaptive feature that may enable animals and plants to live in particular habit. Homework: Assign the following questions as homework. Q. Compare different types of habitats in terms of: region climate special feature animals plants Note: The topic is too long to teach in 45 minute class. So, the teacher can break it into two classes for ease. Lesson 4 Topic: (4.4: Features that allow animals and plants to live in a particle habitats) (4.5: Adaptations of living things to daily and yearly changes in their habitats) Teaching objectives: ⦁ Explain that temperature, water availability, natural disasters, human actives are some features that allow organism to adapt for a particular habitat. ⦁ Explain that animals adapt particular features against harshness of above mentioned features. Key vocabulary: Optimum temperature, water scarcity, drought, flood, fire, earthquakes, migration. Materials required: ⦁ Board (White/Black), chalk/marker, CSS – Science book – 7, Pictures of features as per CSS – Science – 7. Teaching points: Every living being is naturally adaptive to survive in its particular habitat. Every organism have developed features in accordance with temperature and water. He takes action to avoid harsh conditions against which it could not adapt himself. Migration, earth proof housing, air conditions, heaters etc. are such actions and developments which were made against the harshness of environment. 52 Teacher Resource Pack Guide Science 7 Suitable temperature is the most important feature to live in a particular habitat. In aquatic environment it is important in such a way that it maintains the dissolved oxygen level in water. Because at high temperature, oxygen release out of the water. Animals adapt themselves according to winter and summer temperature. Many animals hibernate in winters. Many animals lay and reproduce in summer. Water is also as important as temperature. Life variety is found where water is in abundance. Similarly, condition and intensity of natural disasters greatly influence the organisms’ life. Drought is a period of lesser rainfall than average for longer period of time. It (drought) compels humans to migrate and cause deaths of animals and plants. Flood areas receive rain fall for longer time than average. They also cause loss of life. Same happens when earthquake and fire takes place. Migration results as a result of unsuitable above mentioned conditions. Migration of species reduces the population size in a particular area disturbing the normal ecosystem. Introduction: Ask some questions that may lead students towards the lesson. What would happen if there remain summer through out the year? How would life suffer if water become scarce? What consequences had to bear by people living in earthquake region in 2015? Have you ever seen birds in summer coming from Syria? Why do they do so? After having answers from students, introduce them the today’s topic. Tell them, they would find the answers of these questions more logically in todays lesson. Development: Explain the todays topic. (Teaching points can be helpful). Activity: Then, divide class in groups (9 – 10). Assign one feature to one group. Ask students to read their topic from CSS – Science 7, discuss with peers and then each student will write a paragraph on its findings. Paragraph should cover the following aspects. Why is any particular feature necessary to live suitably in an environment? How does it affect the life? What adaptations are made to avoid its intense form? The teacher will roam about in the class. He / She will help students in writing the paragraph. When students have done, check their work randomly. Share of the some best paragraphs with class. Appreciate students’ efforts. Summaries the lesson by reading it from CSS – Science 7. Homework: Assign following questions as homework. Identify features responsible for survival in a particular habitat. Lesson 5 Topic: (4.6: Adaptations in animals and plants for particular habitat) Teaching objectives: ⦁ Explain to students that animals and plants develop special feature to live in a particular habitat. Key vocabulary: Adaptions, Nocturnal, behaviour, streamlined body. Materials required: ⦁ Board (White/Black), marker/chalk, CSS – Science – 7, charts showing representative animals of different habitat. Teaching points: Plants and animals have lived in the wild for thousands of years. During this course, they have developed adaptations to increase their chances of survival. An adaptation is a change or the process of change by which an organism becomes better suited to its environment. These adaptations can be structural or behavioral. 53 Teacher Resource Pack Guide Science 7 A structural adaption is a physical feature (in the body parts) of an organism that has changed over time or developed over time. Often these develop due to environment of the animal. e.g. A bird has feather to fly, bears have fur to keep them warm in the winter, arctic marine mammals have blubber to keep them warm in the icy water. A behavioral adaptions is something an organisms do to survive. Animals do this as a reaction to the changes in climate in their environment. Bears, snake, frogs hibernate (go into a deep sleep) during coldest months of year. Lions, Jackals, etc. Producing various sounds to warn enemies. These animals and many other produce specific sounds that invite their mates to initiate the reproduction process. These are all behavioral adaptations. Introduction of lesson: Ask students, “What is habitat?” (Ans. A home or environment of living thing where animal/plant live). Ask students to name some habitats. (Ans. Forest, grass land, desert, etc.) Introduce the today’s topic. Tell them many animals had to develop adaptations in order to successfully survive in these different habitats. Tell students that adaptation is a change or the process of change by which an organism becomes better suited to its environment. Activity: Show students pictures of different animals (bear, elephant, lion duck) and have the guess one of the adaptations each animal developed. (Bear have thick hair to keep themselves warm, elephant = long trunk to eat sugarcane, lion = coarse voice, roaring to warn enemies, duck = webbed feet to swim). Tell students adaptations can be sorted into two categories: i. Structural ii. Behavioral Explain structural and behavioral adaptations. (Take help from teaching points and CSS – Science – 7). Tell students behavioral adaptations also include migration and hibernation. Tell students hibernation is when an animal spends the winter sleeping or resting. Show students pictures of animals that hibernate (frog, bear, etc.) Activity / Students engagement: Divide students into small groups. Provide or display the pictures of different animals (Examples: Polar bear, arctic fox, snowy owl, cactus, rainforest tree, lizard, camel, lion, wolf, birds, fish, duck, frog, water lily, tree leaves). Draw the following table on board and ask students to copy it. No. Animal / Plant Habitat Adaptation Purpose of Physical / adaptation Behavioral 1. 2. 3. 4. 5. Ask students to observe the pictures carefully. Separate plants and animals. Identify the habitat of each organism. Try to know the particular adaptation it has developed. Then, try to find out why this particular adaption was made. How is it helpful for the organism? Give students sometime to find out. Allow them to consult CSS – Science 7, book as a reference. Teacher should help students by giving them hint through questioning e.g. How does polar bear protect themselves from intense cold? What is the purpose of feather on the body of snowy owl? (To protect against severe cold). How do desert plants survive when no water is available? (They store water in their stems, have reduced leave to avoid water loss). Trees in rainforest are tall trees to get maximum sunlight. Why is camel said plane of desert. (Due to broad feet and water storing capacity in its stomach). Complete the table on board by students responses as such: 54 Teacher Resource Pack Guide No. Animal / Plant Science 7 Habitat Adaptation Purpose of Physical / adaptation Behavioral 1. Polar bears Cold land Thick fur coat Protection against Physical Arctic fox habitat intense cold 2. Snowy owl Cold land Coat of feather Protection against Physical habitat intense cold 3. Cactus Desert Spiny leaves, Reduced water loss Physical thick fleshy stem Store water 4. Rainforest trees Rainforest Tall trees To get maximum Physical sunlight 5. Water lily Aquatic habit Submerged roots To float easily Physical 6. Camel Desert Large feet and To walk easily on Physical stomach sand, store water 7. Lion Hot land Roaring To warn enemies Behavioral 8. Wolves Hot land Howling To warn enemies Behavioral 9. Fish Aquatic habitat Streamed lined body To swim easily Physical Closure: Revise all the points from board. Homework: Assign following questions as homework. How do animal and plants adapt themselves to live in a particular habitat? Test Exercise – 1 A. 1. Choose the correct answer and fill the circle. The study of interactions that a lion and wolf have with each other, with other organisms and with abiotic components of forest, is termed as: ecology geology geography behavioral biology 2. The role of a plant that it plays in the community is known as: behaviour niche effective role attitude 3. Which habitat posses highly windy, dry and grassy land? tundra habitat arctic habitat grassland habitat deciduous forest habitat 4. Polar bears have white fur that helps them to live in their particular habitats. What is this ability called? alteration adaptation biological rhythm circadian rhythm 5. Why do cactus not grow in summer season? due to less water availability in desert. due to more water availability in desert. due to low sunlight availability in desert. due to low temperature in desert. B. Answer the following questions briefly. 1. Define ecology. Ans: Ecology is the study of interactions that organisms have with each other, other organisms and with abiotic components of their environment. 2. What are the types of forest habitat? Ans: There are three types of forest habitats: i. Deciduous forest ii. Coniferous forests iii. Rain forest 3. Behavioral adaptations are found in living organisms. How do they help animal to live in particular habitat. 55 Teacher Resource Pack Guide Science 7 Ans: Behavioral adaptations are found among living organisms. These kinds of adaptations help them to protect themselves from predators, enemies e.g. roaring of lions, bowling of wolves. Behavioral adaptations help them to initiate the process of reproduction. 4. Day and night affect the plants. Explain. Ans: Light and dark period (day and night) has a significant affect in a habitat on daily basis. Plants particularly prepare their food in day time. They are unable to do photosynthesis during night time. Insects carry out the process of pollination (first step of plant reproduction) during day time. Some plants also bloom in presence of sunlight. 5. How are arctic fox and bear adapted to live in cold climate? Ans: The polar bear and arctic fox are well adapted to their cold habitats. They have thick fur on their bodies. This fur protects their body and keeps them warm in freezing cold. Snowy owl also has a thick coat of feathers. Lesson 6 Topic: (4.7: Respond of living thing to daily environmental conditions) Teaching objectives: ⦁ Explain how do daily environmental conditions help livings organisms. ⦁ Explain that temperature, light and rainfall are effective only in optimum conditions. Key vocabulary: light intensity, chemical energy, biological rhythm, germination, warm blooded animals, drought, flooding. Materials required: ⦁ Board (White/Black), chalk/marker, CSS – Science – 7 book. Note: This lesson would be taught as done in lesson 4. Lesson 7 Topic: (4.8: Food chains) (4.9: Relationship between produces and consumers) Teaching objectives: ⦁ Explain food chain. ⦁ Discuss key factors, processes and components involved in a food chain. ⦁ Identify trophic level of a food chain. ⦁ Explain the relation between producers and consumers. Key vocabulary: Food chain, energy flow, trophic level, terrestrial food chain. Materials required: ⦁ Board (White/Black), chalk/marker, CSS – Science – 7. Picture cards of leaf, caterpillar, rat, owl and arrows. Introduction / Activity: Divide class into small groups. Provide each group picture card of leaf, caterpillar, arrows, rat and owl. Ask them to arrange the pics making a chain by putting arrows on the basis of who eats whom. When students have done, check whether they did it correctly or not. Then draw the food chain by yourself on board. It would be as follow: Plant caterpillar rat owl Ask a volunteer student to explain the links developed then explain it yourself. Tell students it is called a food chain. Tell them that arrows mean ‘is eaten by’ and represent the transfer of energy and nutrient. Explain them that each organism in food chain is a trophic level. Ask students to identify producer and consumer in this food chain. Explain to the students that in a habitat, animals and plants are interdependent. They need each other. Explain that there may be more than one consumer in a food chain. I.e. primary consumer, secondary consumer tertiary consumer, etc. Primary consumer eat plants, secondary consumer eat primary consumer, tertiary consumer eat secondary consumer the chain goes on. At the end, they are eaten by 56 Teacher Resource Pack Guide Science 7 decomposers thus energy that came from sun was utilized by plants, transferred into consumer and then returned back to plants through decomposer. It is called energy flow. Without plant a food chain cannot continue. Activity – 2: Provide a list of terrestrial animals and plants and ask students to construct a food chain. Also indicate what each link is. Whether it is producer, primary consumer or tertiary consumer. Plant, Caterpillar, lizard, snake Activity – 3: Write the name of aquatic organism on board and ask student to construct an aquatic food chain. Phytoplankton, Zooplankton, Fish, Pelican Answers: Summary: Revise the lesson and read it from CSS – Science – 7. Homework: Assign the following question as homework. Why do food chains always begin with a producer? Describe two food chains in two different environments. Note: Lesson 7 (topic 4.10 Food web would be taught by following the Lesson 6). Test Exercise – 2 A. 1. 2. 3. 4. Choose the correct answer and fill the circle. Which of the following abiotic factor promotes growth, flowering and germination in plants? air water light temperature Lion, crow and whale belongs to which of the following category: warm blooded animals cold blooded animals exothermic animals endothermic animals Producers are capable of: photosynthesis respiration catalysis glycolysis If a food chain contains number of organisms, what amount of energy will be available? 57 Teacher Resource Pack Guide lesser Science 7 more fewer larger 5. If five food chains are interconnected, they form: food web energy cycle food cycle energy flow B. Answer the following questions briefly. 1. Trophic level is an energy level. How? Ans: Each trophic level in a food cycle is an energy level. It is said because organisms in each level utilize some amount of energy and transfer the unused / used energy to next trophic level. 2. How does light intensity affect the plants? Ans: Light is required by plants for photosynthesis. Some plants show flowering when they receive required amount of light (intensity). Such plants would not grow if they do not receive the required amount. So, optimum light is necessary for plants growth and germination. 3. Define food chain. Ans: A food chain is defined as a linear link or series of organisms each dependent on the next as a source of food. 4. Food web is formed of interconnected food chains. Explain. Ans: Food web is formed of interconnected food chains. It is so because a single organism can be part of many food chains. An animal/organism is connected to other animals in many ways to help them all survive. 5. Give an example of aquatic food chain. Ans: An aquatic food chain is given below: Phytoplankton zooplankton fish Pelican Review Exercise A. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Choose the correct answer and fill the circle. Choose the basic functional unit of environment: habitat environment ecosystem biome Which of the following habitat posses warmer climate with abundant rainfall? grassland rainforest tundra coniferous forest About one fifth of the Earth's land is covered by: tundra habitat forest habitat grassland habitat sea habitat Most of the African states have below-average rainfall that results in long scarcities in the water supply. What is that condition called? flooding drought earthquake lightening The feature that most of the aquatic plants have is: air spaces less stomata thin leaves thick plant in surface How each living thing gets its food and energy? through food chain through food web through ecosystem through energy cycle What is the best suited name for the process of presence of nutrients and energy flow in living organisms? energy cycle energy flow in food cycle energy in food chain energy in food web In a forest food chain, goat eats: plants animals decomposers plants and animals What will be the place of mammals called in each food chain? trophic level energy level food level organism level In aquatic ecosystem food chain, phytoplankton is eaten by: zooplankton and krill crab fish blue whale 58 Teacher Resource Pack Guide B. 1. Ans: 2. Ans: Science 7 Answer the following questions Briefly: Enlist the biotic factors of an ecosystem. Biotic factors of an ecosystem are: i) producers ii) consumers iii) decomposers Define alpine tundra. Alpine tundra is a type of tundra habitat. In this habitat, due to high altitudes, trees are not present. They have adverse climate. 3. Write the relation between producer and consumer. Ans: Consumers depend upon producers for food and energy. In turn, consumers when died, provide nutrients to producers. 4. What is the lowest trophic level of food web? Ans: Lowest trophic level of food web is plant. 5. Write down an example of terrestrial food chain. Ans: A terrestrial food chain is given below: Plant Caterpillar Lizard Snake C. Answer these questions in detail. 1. Compare the different kinds of habitats. Investigate the various features that allow animals and plants to live in a particular habitat. Ans: There are many different kinds of habitats. It can be as big as forest (for lions) or as small as a leaf (for butterfly eggs). To survive in an environment, different organisms require different physical conditions. For example, goldfish needs fresh water whereas, whale needs sea water to live in. Humans on land can survive in more than one habitats whereas, fish only survives in one habitat (water). Every living organism is naturally adapted to the conditions of its particular habitat. For example, in Arctic habitat, a rattle snake cannot live for very long time whereas a walrus cannot live in desert. The different kinds of habitats are forest habitat, desert habitat, fresh water habitat, sea habitat, grassland habitat and tundra habitat. Forest habitat: A type of habitat with abundant trees, plants and animals covering larger area is called a forest. Forests provide shade to the living organisms. They also provide shelter to different animals (butterflies, snakes, bats, lizards, frogs, wolves, parrots, cats and lions). Forest can also be of different types: i. Deciduous forests: Deciduous forests are forest in cool rainy areas. It is necessary for animals to adjust themselves in extreme weathers i.e. cold winters and hot summers. Black bear, grey squirrels, rat snake and turkey are the examples of animals living in deciduous forests. ii. Coniferous forests: Coniferous forests are mostly found in Canada and Europe. The largest type of habitat in world is Taiga that are northern coniferous forests. The cold weather in this type of forest, make it very difficult to survive for living organisms. Squirrels, loon and hawk owl are abundantly seen here. iii. Rain forest: Regions near to equator have a very special type of forest called rain forests. They are warmer but abundant rainfall is their extreme feature. They have long trees with many animals inhabiting on them. Desert habitat: Desert is special type of habitat with driest and hottest climate. They are the regions with least rainfall rate. There are two different types of desert: i. Hot and dry deserts are found near the tropic of cancer or tropic of Capricorn. They have cacti and euphorbia in plants and lizards, snakes, kangaroo rats and camels in animals mainly. ii. Cold deserts are near the Arctic zone of the world. They mainly have antelope and kangaroo rats. Fresh water habitat: There are some animals and plants who cannot survive anywhere else except water. Fresh water habitats are ponds or rivers. Rivers have different fish, algae and 59 Teacher Resource Pack Guide Science 7 mosses so they are full of life. They provide shelter, food and water to aquatic life. Ponds are also full of fishes, wolf spiders, snails, frogs and various other microorganisms. Sea habitat: Habitats made up of salt water are sea habitats. Sea contains different creatures. Some are huge (Sharks, whales or kelps) whereas some are small (small fish and green algae). Grassland habitat: Grassland habitat is quite big, relatively dry area that is highly windy and grassy. Grassland covers about quarter of Earth's land surface area. They do not possess trees or heavy bushes. They mostly have grazing animals like giraffe, zebra or ostrich. There are two different types of grasslands: i. Temperate grasslands are having two extreme weathers: cold winters and hot summers. They are distant from the equator. ii. Tropical grasslands remain hot throughout the year. They are closest to the equator. Tundra Habitat: Tundra are located at high altitudes on mountains around the world. About one fifth of the Earth's land is Tundra. The main types of tundra are Arctic tundra and Alpine tundra. i. The Arctic tundra is frozen for much of the year. The ground is permanently frozen about 10 feet down so the trees cannot grow there. Flies, mosquitoes, polar bear, wolves, snow birds, flat fish are abundantly present in this habitat. ii. Alpine tundra does not contain trees because it is at high altitude. The high altitude causes an adverse climate, which is too cold and windy to support any tree growth. Mammals like mountain goats, sheep and elk, grouse like birds, beetles, grasshoppers and butterflies are mainly found in this region. 2. Identify the factors that cause daily and yearly changes in a habitat. Ans: Each and every living organism is naturally adapted to survive and live in its particular habitat. They have well adaptive features regarding temperature, water availability, nature of soil etc. Any change in these factors cause huge changes in the populations of a habitat. Many other natural and man-made factors also cause changes in habitats. Plants (as producers) utilize light energy from Sun to make their own food. All other living organisms depend directly or indirectly on green plants for food. Animals also need light for their survival i.e. peacock absorbs sunlight to warm its body. Light intensity also affects like suitable temperature and natural disaster the number of plants in a habitat. If the number of plants decrease due to unavailability of light, there will be a decline in number of animals as well. Here are some other factors that affect the life. Suitable temperature: It also causes change in the population of a habitat. Any unusual increase or decrease in temperature can disturb the habitat. For example, there will be less oxygen available to aquatic life in warm water so aquatic life would be threatened. Moreover, at high temperatures in deserts, human life and its concerned activities are nearly impossible to be done. Water: it is necessary for existence of life. In abundance of water, there will be more variety of life. Availability of water in a habitat greatly affects its organisms. Natural disasters: Natural disasters also bring changes in habitats. They may be droughts, floods, lightening and earthquakes etc. Drought: A drought is a period of below-average rainfall in an area that results in long scarcities in the water supply. All water reservoirs dry up during a condition of drought. Most plants and animals die or migrate to other places. Flood: An area is considered as flooded when it gets a lot of rain for a long time. Many plants and animals die or migrate to dry places during a flood. Fire: Sometimes, lightning strikes a tree that causes forest fires. Plants and trees are burnt instantly. Many animals are also at risk to die. It takes a longer period for a tree to grow back. Earthquakes: The shaking of surface of Earth is known as earthquake. They can destruct a habitat rapidly. On 26 October 2015, a 7.5 magnitude earthquake hit major cities of Pakistan, 60 Teacher Resource Pack Guide Science 7 including the northern areas leaving at least 200 dead and more than 1,000 injured due to building collapses, landslides and other earthquake related incidents. Other factors: Human activities also cause changes in different habitats. Forests are the habitat of various animals and birds. Farmers cut down forests for farming. They also cut down trees to get wood or paper for export. In any of the way, the natural habitats of many plants and animals is being destroyed. Pollution also troubles the air, land or water. Air, water, noise or land pollution are, directly and indirectly, damaging the lives and habitats of humans, animals and plants. Migration: Another important factor that can change the size of a population of a habitat is migration. Due to water shortage or under harsh environmental conditions, organisms migrate to better living places. When individuals leave an area, it decreases the size of the population in that area and vice versa. 3. How living things adapt to daily and yearly changes in their habitat? Ans: Light and dark period (day and night) has a significant affect in a habitat on daily basis. Plants particularly prepare their food in day time. They are unable to do photosynthesis during night time. Insects carry out the process of pollination (first step of plant reproduction) during day time. Some plants also bloom in presence of sunlight. They release most of the carbon dioxide produced during night time. Most of the birds, animals and insects are mainly active during day time for getting their food. Some other animals like bat, owl, cats and dogs are also remain active during night time. They tend to avoid any competition with day-time active animals. Summers and winters also have great influence on organisms living in a habitat. Animals and plants have adapted reproductive cycles according to environmental conditions i.e. water, temperature etc. Many animals hibernate in the winters like bees, snakes, lizards, bears, frogs and bats etc. to save themselves from harsh cold weather. These animals come out in spring season again to get food. The best example of the season influenced reproductive cycle is of frog. They hibernate in winters, come out in spring, reproduce in rainy season, help their young ones to grow in coming months and again hibernate in next winters. Birds and mammals are also influenced by seasons. Mammals especially humans drink plenty of water in summers and face sweating. Availability of water in deserts also affect the reproductive cycles of desert plants like cactus. They do not grow in summer season. Their reproductive cycle starts in spring season when they produce seeds. Seeds tend to grow in rainy season and plants die before summers again. Most of the birds also reproduce in spring season and their young ones grow before hot summers. Fish and aquatic animals and plants also follow the same pattern. They reproduce and grow in spring season before the arrival of hot summers or cold winters. 4. Write down the ways in which living things respond to changes in daily environmental conditions such as light intensity, temperature and rainfall. Ans: Our planet has suitable conditions for living organisms to grow, reproduce and flourish. These are all suitable conditions for healthy living on the planet. These conditions require both living and nonliving organisms. The environmental conditions such as light intensity, temperature and rainfall of a habitat tends to change daily life patterns and thus the respond of living things to them is also change. Light intensity: Natural light is utilized by plants for the process of photosynthesis where light energy is converted into chemical energy. It is also important for their growth, flowering and germination. Plants as producers transfer energy to all animals (consumers) indirectly as their food source. For animals, the intensity of light affects their skin colour and sight. There are insects that use sunlight to differentiate between flowers. Light not only is an energy source but an important factor for maintaining the biological rhythm of life. If there will be no light available, all the functions of life will be stopped. This will eventually lead to the massive death rate of living organisms. Temperature: All living organisms are well adapted to survive in a moderate range of temperatures. Living organisms are naturally adapted to live in normal temperature range. Many organisms live in extreme cold or extreme hot temperature ranges. Cold blooded animals like fishes vary their body 61 Teacher Resource Pack Guide Science 7 temperature based upon their surrounding conditions. Warm blooded animals like mammals can easily maintain and regulate their body temperature in any surrounding environment. In either extreme cases, if a species faces harsh condition, species will tend to migrate or will die. Rainfall: Living organisms (animals and plants) need certain amount of water. It regulates the temperature of human body. It helps in normalizing the pressure of blood. It is present in the form of saliva, sweat or tears in human body. Plants also possess nutrients throughout their body. If water availability deviates from its original amount in a habitat, the species will be unable to survive. Drought and flooding are both devastating forms of extreme change in amount of rainfall. In both cases, either the species will be forced to migrate or they will die. In conclusion, every living organism requires moderate temperature, water and sunlight in their particular habitat. Perfect living conditions only exist when moderate amount of each factor is available. If the balance of each factor is not maintained, then the natural phenomenon of life would be disrupted. 5. Why do food chains always begin with a producer? Illustrate the relationship between producers and consumers? Ans: All food chains start with energy from the Sun. This energy is captured by plants. Thus, the living part of a food chain always starts with plant life (producers) and ends with an animal (consumer or decomposer). Some animals eat plants (herbivores) and some animals eat other animals (carnivores or omnivores). A producer produces food. A consumer consumes food produced by the producer or eats the producer as food source. A consumer may also eat other consumers as food. Without a producer, the consumers will die. There will be no food chain or food cycle without producers and consumers. Each of the two are essential pillars of a food chain. In a food chain, producers are capable of photosynthesis while consumers use respiration. Producers make complex organic molecules, while consumers break them down into simpler ones (say, sugars to carbon dioxide, etc.). Producers concentrate energy into complex molecules, while the consumers convert them into simpler molecules and also get energy as a by-product. 6. Describe two food chains in the two different environments. Ans: Two food chains in the environment: The place of organisms in each food chain is known as its trophic level. The energy is maximum in lowest trophic level and minimum in highest trophic level. So we can conclude that “the larger the food chain, lesser will be the energy available and vice versa”. Two Food Chains 62 Teacher Resource Pack Guide Science 7 Model Paper No. 1 Section – A: Multiple Choice Questions Marks: 40 Time: 50 Minutes Roll No. __________ Choose the correct option. 40 1. Peristalsis is the movement that move the food intake. In which of the following organ, it does not take place? stomach large intestine small intestine mouth 2. Identify the factor that does not lead to diarrhea. low fiber diet stress bacteria alcohol 3. During exhalation, intercostal muscles move: upward downward leftward rightward 4. Bile helps in the digestion of: protein carbohydrate water fats 5. In which of these parts of large intestine, stool is present? colon caecum rectum none of these 6. How does small intestine contribute in segmentation? by chewing food by churning food by segmentation by assimilation 7. Cellular respiration takes place an/at: cytoplasm mitochondria Golgi apparatus nucleus 8. When diaphragm relax, it moves: upward downward rightward leftward 9. The energy producing process in humans is: digestion breathing respiration circulation 10. Pneumonia affects the: bronchial tubes trachea alveoli all of these 11. The receiving chamber for blood into the heart is: aorta right ventricles left ventricle auricles 12. Vena cava transport blood: into the heart out of the heart into lungs out of the lungs 13. In veins, pressure of blood is: lower higher normal no pressure 14. The statement not true about pulmonary artery is: it carry blood to lungs it carries deoxygenated blood it receives blood from right ventricle It carries oxygenated blood. 15. By-pass surgery is done to cure: arteries of the body arteries in heart veins of the body veins in heart 16. Water is absorbed by root hours through the process of: transpiration osmosis respiration diffusion 17. The structure responsible for water transportation in plant is: phloem xylem root hair stomata 18. Water loss in leaves is prevented by: stomata guard cells cuticle all of these 19. Translocation takes place in: xylem phloem mesophyll cells chloroplast 63 Teacher Resource Pack Guide 20. Science 7 If rate of transpiration increase, rate of absorption of water: increases does not change decreases stops 21. Identify the plant that grown by asexual reproduction: rose banana maize pea 22. Which of the following pollen are transported by wind? light and dry light and wet heavy and dry heavy and wet 23. Flowering plants transfer genetic information through: budding seeds spores laying 24. Which one of the following does not contribute in seed formation? pollen ovule ovary spore 25. The most important purpose of colourful petals is: beautification generate fragrance attract pollinators protect ovary 26. Seed forming procedure is: pollination fertilization laying none of these 27. Cross-pollinated plant: tomato beans pea all of these 28. The plants show more variations in characters that observe: self-pollination spore formation vegetative reproduction cross-pollination 29. Vegetative reproduction produce plants from: root stem leaves all of these 30. Lower plants reproduce through: sexually asexually self-pollination none of these 31. The plants found in grassland habitat are: tall trees coniferous trees bushes algae only 32. In which of the following habitat, trees do not grow? desert sea habitat cold desert tundra 33. Tundra are located an/in: high altitude low altitude equator oceans 34. Food chains always start from: sun plants animals decomposers 35. Organisms make adaptations for to: eat more survival reproduce make friend 36. In large food chains, the available energy is: higher lesser intense scarce 37. Plant mouse snake eagle bacteria Identify the tertiary consumer from the above given food chain: mouse snake eagle bacteria 38. Light is necessary for plant for: flowering growth germination all of the above 39. The basic functional unit of environment is: environment ecosystem habitat biome 40. Spiny leaves in desert plants is an adaptation against: high temperature low temperature water scarcity food shortage Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) Define digestive system. (2) 64 Teacher Resource Pack Guide Science 7 (b) (c) Q.2: What is epiglottis? How does it help in digestion? (2) Describe the functions of small intestine. (2) Describe the function of each. (1 mark each) No. Structure Function 1. Aorta 2. Superior vena cava 3. Inferior vena cava 4. Pulmonary vein 5. Pulmonary artery 6. Tricuspid valve Q.3: (a) Write the causative agents of the following: (2) (i) Pneumonia __________ (ii) Tuberculosis __________ (b) How is breathing process different from burning process? Give at least points 4. No. Respiration Burning Q.4: (a) Name the process taking place in the given structures: (i) Xylum __________ (ii) Phloem __________ (b) Differentiate between larynx and pharynx. No. Larynx Pharynx (2) (c) Q.5: (2) (2) How does structure of a leaf facilitate gaseous exchange. How is asexual reproduction different from sexual reproduction? No. Asexual reproduction Sexual reproduction 1. 2. 3. 4. 5. 6. Q.6: (a) Define fertilization. (b) Explain the process of fertilization by drawing the diagram. (c) Name the structure that develops into ovule. Q.7: (a) Construct a food web from the following food chains. (i) grass slug sparrow cat (ii) grass slug fox (iii) grass rabbit fox (iv) grass rabbit cat (v) grass sparrow cat (b) Name the producer in this food web. Q.8: (a) Define food chain. 65 (2) (2) (3) (1) (5) (1) (2) Teacher Resource Pack Guide Science 7 (b) A food chain is given below. Which of the trophic level can be eliminated in such a way not to affect the continuity of energy flow? (2) Algae caterpillar bird snake owl bacteria (c) Give reason for you above made elimination. (2) Q.9: (a) Define habitat. (2) (b) Write two adaptations to live in desert habitat. (i) __________ (ii) __________ (c) Name two abiotic factors that may affect a habitat. (2) Q.10: (a) Draw a well labeled diagram of heart. (4) (b) Describe at least two functions of heart. (2) Model Paper No. 2 Section – A: Multiple Choice Questions Marks: 40 Time: 50 Minutes Roll No. __________ Choose the correct option. 40 1. The protein present in food digests in: mouth stomach small intestine large intestine 2. Absorption of nutrients from digested food takes place in: duodenum jejunum caecum rectum 3. Dry cough, chest pain, fever and trouble in breathing? Identify the disease from the following symptoms. asthma pneumonia tuberculosis lung cancer 4. Identify the function of gall bladder. store excess bile secrete bile secrete digestive enzymes absorption of water 5. In which of the following organ, water is absorbed? gall bladder small intestine large intestine liver 6. Hydrochloric acid helps in digestion of: carbohydrates lipids vitamins proteins 7. Bronchi open into: trachea lungs esophagus stomach 8. During inhalation, diaphragm moves: upward down ward leftward rightward 9. Which of the following thing is not produced as a result of respiration? oxygen carbon dioxide energy water 10. Identify the organ affected by asthma: alveoli lungs bronchial tubes all of these 11. Identify the structure that connects the vessels of oxygenated blood and deoxygenated blood: arteries veins capillaries aorta 12. The technique used to examine arteries is: ECG X-ray angiography none of these 13. Blood in pulmonary vein is: oxygenated deoxygenated at low pressure none of these 14. Blood pressure in arteries is: normal low high fluctuating 15. The number of valves in our heart is: 66 Teacher Resource Pack Guide 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. Science 7 two four six eight Plant cells maintain their rigidity due to: nutrients carbon dioxide oxygen water The disease causing high glucose level in blood is: high blood pressure anemia heart attack diabetes Most of the absorption in roots takes place through: primary root secondary root tertiary root root hair Gases in leaves are absorbed by: stomata xylum cell phloem cell mesophyll cell The process for food transpiration is: translocation transpiration respiration evaporation If a flower only have carpel and lack stamen, how will it develop seed? by self-pollination does not produce fruit by cross-pollination all of these The structure produced right after fertilization is: embryo zygote fruit seed Pollen grains enter into ovary through: filament anther style pollen tube Wind pollinated plant is: lily eel-grass lettuce pine Insect pollinators visit flower for: pollen fragrant oil shelter nectar Rose grow through: sexual reproduction laying fragmentation cutting Budding phenomenon is shown by: jasmine rose tulip cactus The structure that develops into fruit is: ovary ovule pollen embryo The chances of variations in characters is high in plants that grow by: asexual reproduction self-pollination cross-pollination spores The upper part of ovary is: style stigma filament anther Identify the secondary consumer: cow goat lion caterpillar Sharks and whales are found in: sea habitat freshwater habitat rivers all of the above The animals that can maintain their body temperature are called: warm blooded animals cold blooded animals strong animals active animals Identify the correct relation: producers decomposers consumers decomposers producers consumers producers consumers decomposers consumers producers decomposers The special feature in coniferous forests is: heavy rain cold weather small trees hot weather 67 Teacher Resource Pack Guide Science 7 36. The inhabitants of grassland habitat are: fish nocturnal grazing animals all of these 37. The factor that cause migration is/are: fire earthquake harsh environment all of these 38. Population in an area decrease due to: moderate temperature average rainfall food availability flood 39. The adaptation for hot land habitat is: thick fur streamed line body webbed feet fleshy stem 40. The feature that most of the aquatic plants have is: air spaces less stomata thin leaves thick plant surface Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) Name the nutrients that is assimilated by following enzymes. (4) (i) salivary amylase __________ (ii) Pepsin __________ (iii) Bile __________ (iv) Pancreatic Juice __________ (b) Define chemical digestion. (2) Q.2: (a) Define breathing. (2) (b) Differentiate between inhalation and exhalation. (at least 2 points for each) (4) No. Structure Function Q.3: (a) What is constipation? (b) Describe the factors leading to constipation. (at least – 3) (c) How could constipation be prevented. Q.4: (a) Define transport system. (b) Name the four chambers of heart. Also describe their function. Q.5: (a) Define diffusion. (b) Draw a flow sheet showing the transport route in plants. (c) How does transpiration contribute in mineral transportation? Q.6: (a) Define pollination. (b) Differentiate between self-pollination and cross pollination. No. Self-Pollination Cross Pollination (1) (3) (2) (2) (4) (2) (2) (2) (2) (3) (c) Why do insects visit flowers? Q.7: (a) What is asexual reproduction? (b) Write down different modes of asexual reproduction. (i) __________ (ii) __________ (iii) __________ (iv) __________ (c) What is/are demerits of asexual reproduction? Q.8: (a) Define the term population. (b) Name the factors that may affect the population in a habitat. (c) How do human activities affect the population of a habitat? (1) (2) (2) 68 (at least – 4) (at least – 4) (2) (2) (2) (2) Teacher Resource Pack Guide Science 7 Q.9: (a) Define adaptation. (b) How do behavioral adaptations help organisms to survive. (c) Describe at least two behavioral adaptations in organisms. Q.10: (a) What is a trophic level? (b) Here, a food chain is given. Identify and write each trophic level. Plant caterpillar mouse snake eagle mushroom (c) Why does each food chain start with plants? (2) (2) (2) (1) (4) (1) Model Paper No. 3 Section – A: Multiple Choice Questions Marks: 40 Time: 50 Minutes Roll No. __________ Choose the correct option. 40 1. Which of the following is not the function of small intestine? breaking down of food absorption of useful nutrients digestion of lipids total removal of water 2. Breakdown of food bites into small pieces is known as: mechanical digestion chemical digestion grinding assimilation 3. Identify the disease from its symptoms given below: Chill coughing, weight loss, fatigue, fever, night sweats lung cancer pneumonia asthma T.B 4. Identify the enzyme that digests protein: bile salivary amylase pepsin none of these 5. Stomach secretes: pepsin bile hydrochloric acid all of these 6. Bolus is: food + water food + saliva food + hydrochloric acid digested food + undigested food 7. Chemotherapy is used for the treatment of: pneumonia lung TB asthma 8. In the process of respiration, glucose in provided by: respiratory system digestive system nervous system skeletal system 9. Inhaled air is filtered in/at: nose larynx lungs bronchi 10. Diaphragm is present: at bottom of lungs above the lungs behind the lungs in front of lungs 11. Heart provides oxygenated blood to the body through: superior vena cava pulmonary artery aorta pulmonary vein 12. Location of pacemaker is: right atrium right ventricle left atrium left ventricle 13. The causes of high blood pressure is/are: high glucose high cholesterol blood clotting all of these 14. The blood vessels having low pressure blood are: arteries veins capillaries both (a) and (b) 15. By-pass surgery is done for the treatment of: veins inside heart veins outside heart arteries inside heart veins outside heart 69 Teacher Resource Pack Guide 16. 17. 18. 19. 20. 21. 22. 23. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. Science 7 The cells responsible for gaseous exchange in leaves are: xylem cells phloem cells mesophyll cell stomata Due to transpiration of water, temperature of leaves: increases decreases remain normal does not affect Number of stomata on upper surface of leaves is: great less greater lesser Water in stem moves upward by: diffusion osmosis transpirational pull all of these The food production site in plants is: root stem leaf flower Pollen grain producers in: sepal carpel style stamen Which of the following is not the characteristics of: large no of off springs single parent involve genetic variations found fast process Spore bearing organs are present in: rose flowering plants jasmine non-flowering plants Identify the non-vegetative organ: stem root leaf flower The pollens that are dry and light are pollinated by: insects birds water wind Sexual reproduction in plants begin by: fertilization flower production pollination spore formation The pollination that involve only one flower is: valves chambers capillaries pericardium Cross pollination happens through: insects birds water all of these Primary consumer are always: decomposers herbivores carnivores omnivore Plant grasshopper bird fungi. Identify the decomposer from the above food chain. grasshopper mushroom plant all of these A specific area in which an organism lives is called its: home country habitat ecosystem Rainforest are found near: northern hemisphere southern hemisphere equator none of these The frozen habitat is: tundra grass land coniferous forests none of these Habitats are different from one another due to difference in: climatic conditions animals plants air Cacti grow in: forests deserts tundra grass lands Plants can’t grow in tundra habitat because of: adverse climate water scarcity abundant rainfall infertile soil 70 Teacher Resource Pack Guide 39. 40. Science 7 The seasonal adaptations is: hibernation nocturnal habitat pollination both (b) and (c) Stream – lined body of fish help them: in swimming in laying egg in food searching against enemies Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) Define digestion. (2) (b) Describe the role of saliva in digestion. (2) (c) How does liver help in digestion. (3) Q.2: (a) Define physical digestion. (2) (b) Where does physical and chemical digestion take place? (Name (at least) two organs for each type) (4) Q.3: (a) Define cellular respiration. (2) (b) Describe the mechanism of cellular respiration. (3) (c) What is ATP? (1) Q.4: (a) What is deoxygenated blood? (2) (b) How do lungs purify the blood? (2) (c) Name the 2 blood vessels that provide and receive blood from lungs. (2) Q.5: (a) Describe at least one function of arteries, veins and capillaries. (3) (b) How does diet cause high blood pressure. (3) Q.6: (a) Draw labeled structure of guard cell and stomata. (2) (b) Differentiate between xylem and phloem vessels. (4) No. Xylem vessel Phloem vessel Q.7: (a) Define sexual reproduction. (2) (b) Describe at least three features of sexual reproduction. (3) (c) In which plants sexual reproduction take place? (1) Q.8: (a) What is reproduction? (1) (b) Explain vegetative reproduction. (2) (c) How does fertilization take place in plants? (3) Q.9: (a) Define adaptation. Describe with the help of diagram. (2) (b) Describe two adaptations for aquatic habitat. (2) (c) Define food chain. (2) Q.10: (a) Classify the following organisms into producers, consumers and decomposers. (6) (bacteria, grass, goat, fungi, coniferous tree, lion) ‘Detailed Division of Syllabus’ 2nd term Week 1 Day 1 Day 2 Day 3 Day 4 71 Unit– 5 T – 5.1: T – 5.2: T – 5.3: T – 5.4: T – 5.5: T – 5.6: Water Water for life Sources of water Impurities of water Water Processing (a) Water Treatment Stage – 1: Pre-treatment Uses of Water in Pakistan Water Conservation Teacher Resource Pack Guide Science 7 Day 5 Day 6 Review Exercise Review Exercise Week 2 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Unit– 6 T – 6.1: T – 6.2: T – 6.3: Revision of Unit – 5 Revision of Unit – 5 Structure of an atom Structure of an atom Atomic number and Mass number Electronic Configuration T – 6.4: T – 6.4.1: T – 6.4.2: T – 6.5: T – 6.6: T – 6.7: Test exercise – 1 Valency and Ions Valency Ion Isotopes Molecules and chemical formula Law of Constant composition Unit– 7 Test exercise – 2 Review exercise Review exercise Revision of Unit – 6 Revision of Unit – 6 Physical & chemical changes & process Day 1 T – 7.1: T – 7.1.1: Physical and chemical changes Physical changes Day 2 T – 7.1.2: Chemical changes Day 3 T – 7.1.3: Comparison of physical and chemical change Week 3 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 4 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 5 Day 4 Day 5 Day 6 Week 6 Day 1 Day 2 Day 3 Day 4 72 T – 7.2: T – 7.2.1: T – 7.2.2: T – 7.2.3: T – 7.2.4: Why are chemical changes important? Use of hydrocarbons as full Vegetable fat is a gift of chemical change Use of fertilizers in agriculture Plastics T – 7.3: Reversible and Irreversible reactions Review exercise Review exercise Revision of Unit – 7 Teacher Resource Pack Guide Day 5 Day 6 Week 7 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 8 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 9 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 10 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 11 Day 1 Day 2 Day 3 Day 4 Day 5 73 Science 7 Unit – 8: Revision of Unit – 7 Transmission of heat T – 8.1: T – 8.2: T – 8.2.1: T – 8.2.2: T – 8.2.3: T – 8.3: T – 8.4: The cause of flow of heat Modes of flow of heat Conduction Convection Radiation Flow of heat in the Environment Everyday applications of conduction, convection and radiation T – 8.5: Unit – 9: Vacuum Flask Review exercise Review exercise Revision of Unit – 8 Revision of Unit – 8 Dispersion of light T – 9.1: T – 9.2: T – 9.2.3: T – 9.3: T – 9.4: T – 9.4.1: T – 9.4.2: T – 9.4.3: T – 9.4.4: Refraction Law of refraction Refractive Index Effects of Refraction Dispersion of Light Spectrum and Rainbow Colours Uses of Colours and Coloured Lights Three chip video camera T – 9.5: T – 9.6: T – 9.7: Unit – 10: T – 10.1: T – 10.2: Test exercise – 1 Total Internal Reflection Applications of Total Internal Reflection Total Internal Reflection Review exercise Review exercise Revision of Unit – 9 Revision of Unit – 9 Circuit and electric current Transverse and Longitudinal Waves Wave Terms Teacher Resource Pack Guide Day 6 Week 12 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Science 7 T – 10.3: T – 10.3.1: Characteristics of Sound Factors that affect sound T – 10.4: Applications of Sound Review exercise Review exercise Revision of Unit – 10 Revision of Unit – 10 Revision of Unit – 5 Week 13 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Revision of Unit – 5 Revision of Unit – 6 Revision of Unit – 6 Revision of Unit – 7 Revision of Unit – 7 Revision of Unit – 8 Week 14 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Revision of Unit – 8 Revision of Unit – 9 Revision of Unit – 9 Revision of Unit – 10 Revision of Unit – 10 Test of all Units 2nd Term Unit # 5 WATER Lesson 1 Topic: (5.1: Water for life) Teaching objectives: ⦁ Introduce water as the largest treasure of mankind. ⦁ Describe the ways in which clean water is vital for meeting the needs of humans and other living things. Key vocabulary: Hydrosphere’s, homeostasis photosynthesis, Water cycle. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Globe, Display pictures of Earth, (showing water division), Beaker, leaves, Red food color, water. Introduction: The earth in divided into three spheres which support life on it. Lithosphere (Land), Atmosphere (Air) and Hydrosphere (Water). Tell the students that earth looks blue from the space and show its picture. The blue colour appears because earth reflects blue light due to the presence of water. 70% of the earth surface is covered with water. Sea, oceans, rivers, lakes, ice caps and glaciers are the main reservoirs of water. The survival of life on earth is possible only due to the presence of water. Tell students that water, plants, animals, fossil fuels, air etc. are necessary resources for life, but water is the largest treasure mankind has inherited from nature. Water is necessary element for life. Tell the students that life is not present on other planets due to the absence of water. 74 Teacher Resource Pack Guide Science 7 Warm up the students: First ask from students about the importance of water for life, for human beings, for plants. Also ask from them about the general uses of water in houses, industries and agriculture. (As students have prior knowledge about importance of water, they most probably give many answers). Water and life: Tell the students that our body is made up of 70% water. Infect all living things mostly consists of water. All the life processes going on, in the living body need water. In circulatory system, it helps in blood flow through the blood vessels; it assists in the distribution of minerals and nutrients throughout the body. It also helps in the removal of waste matter from the body like urea gets eliminated from the body via excretory system. Many chemical reactions are continuously going on in our body. These chemical reactions also require water as medium. Water also helps in the maintenance of internal body conditions like temperature. This mechanism is known as homeostasis. Take a look at the distribution of water in the human body in Fig. 5.1. Water is not only necessary for animals but it also plays a key role in the transportation of dissolved nutrients and food from roots to the top most leaf. Activity Show the transport of water in leaves. 1. Collect some leaves with white patches or veins. 2. Take the beaker with water and add red food color. 3. Dip leaves in the water. Water rises up in the leaves after 24 or 36 hrs. 4. Show the students. Provide support to the plant structure by making them turgid. Turgidity is due to high water content which keeps plant cells upright. Ask from students why plants leaves become flaccid in summer but become normal upright when water? Water makes food: Living beings also need food for their survival besides water. The primary source of food on our planet earth is plants. Plants not only need water for their life activities but they also need water for the preparation of food. The preparation process of food is known as photosynthesis which requires water as basic ingredient. Carbon dioxide + water Glucose + water + oxygen. The glucose stored in plants in fruits, vegetables and seeds used by human beings and animals as their food source. Water provides habitat: Water is home for many living organisms. Millions of fishes and other aquatic animals are living in seas, oceans and rivers. These oceans and rivers are also the home of many aquatic plants. Activity Show the picture of water ecosystem. Water in houses: Water is used in home for different purposes. It is used for cooking of food, washing of our clothes, cars, houses etc. Ask from students about other uses of water at home. Water runs industry: Teacher must introduce the idea of industries in mind of students. Industrial and production units are the big users of water. They require water: as a raw material for manufacturing of different materials. as solvent to dissolve different materials. as coolant to cool various parts of machinery. as a transport agent. as an energy source to run turbines for electricity production. Water and environment: Water is not only important for living things but it is also important in the maintenance of entire ecosystem. Ask from students about the maintenance of ecosystem by water balance. Take their views then discuss the following points. Waster helps in the maintenance of Earth’s temperature. Water vapours present in the atmosphere absorb the heat of the Sun and control temperature. Water cycle (The cycle describes how water evaporates from the surface of the earth, rises into the atmosphere, cools and condenses into rain or show in clouds, and falls again to the surface as precipitate) not only maintains temperature but it also regulates the amount of water on earth. Activity: Show the diagram of water cycle and discuss. The rain water when rolls down from the hills carry the sediments into rivers forming valleys. These valleys then provide fertile land for agriculture purpose. In Polar Regions, water in the form of the caps effects climate and cause geographical changes. 75 Teacher Resource Pack Guide Science 7 Not only water but clean water: As we discussed above, water is a necessary element for life, but life needs clean water. Polluted water is unfit for human beings because it causes dangerous diseases like typhoid, hepatitis, cholera. Polluted water when used for irrigation, plants may become unable to produce food. Similarly, the polluted water is used for livestock; it can affect meat and dairy products. Aquatic life also disturbs due to polluted water, because pollution reduces the level of oxygen in water and aquatic life suffers from suffocation. (Discuss the need of clean water in points). Homework: Assign the following questions as homework. 1. What are the main uses of water in industry? 2. How water makes food for plants? 3. How in water important for plants? Conclusion: The teacher should revise all the main points from board regarding need of clean water. Tell them today they have learnt about need of water for life and tomorrow will explore about the resources of water. Lesson 2 Topic: (5.2: Sources of water) Teaching objectives: ⦁ Different sources of water present on the earth. Key vocabulary: Ocean water resources, Fresh water resources, salt water, sweet water, ground water. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Chart showing graphical distribution of water, oceans, lakes, wells, glaciers, ice cycle caps, beakers, stones, soil, sand, water. Introduction: Begin the lesson by revision from last lecture: Do you remember about the uses of water? Why is clean water necessary for life? Then announce in the class that now we study the sources of water present on Earth. As we discuss in previous lesson that 70% of the Earth’s surface in covered with water. The water is present in different forms and locations like on the surface, below the ground, in the oceans etc. We will discuss each source one by one. Mainly, the water is categorized as: (a) Ocean water resources (b) Fresh water resources These resources are the part of water cycle. Water gets evaporates from these resources, rises up into the atmosphere in the form of water vapours, cools and condense back into water and falls again as rain or snow on earth’s surface. This cycle in also known as hydrological cycle. Activity: Discuss the diagram of water cycle with class. Show the diagram and ask the steps from class. The Water Cycle 76 Teacher Resource Pack Guide Science 7 Ocean water resources: The largest reservoirs of water are oceans. These are generally termed as “Salt water” because of high concentration of dissolved salts and minerals dissolved in it. This largest resource is divided into seven oceans throughout the Earth and accounts 97% of total water resources on earth. Ocean water is not suitable for drinking because high amount of salts present in it make it saltish. Ocean water, however, is used for various other purposes for example, for transportation, trade, generation of electricity, tele-communication, as food source, etc. Ocean water also helps in the maintenance of earth’s temperature. Pakistan shares ocean water boundaries in Arabian Sea on its north which is the part of Indian Ocean. Activity Show the pictures of oceans and seas. Fresh water resources: Fresh water is generally termed as “sweet water” because it has low concentration of dissolved salts and minerals. It is the water essential for human use such as drinking, agriculture, manufacturing. Fresh water is present in very small amount, just 2.5% of total water resource. Most of the fresh water is frozen in the form of glaciers and ice caps around North and South poles. Thus it is also not available for use. The remaining fresh water is mainly found as ground water and as running water. The running fresh water is available in the forms of rivers, lakes, swamps etc. Fresh water sources in Pakistan mainly depends upon Indus water system and its tributaries i.e. Jhelum, Chenab, Beas, Sutlej, Ravi. Activity: Show the picture of fresh water resources like rivers, lakes, swamps etc. If some fresh water resource is present in nearby location, give its reference. Revise the idea of “salt water” and “sweet water” again. Ask from students about the difference of salt water and sweet water. Write on the board in the form of points. Ground water resources: The largest useable proportion of fresh water is in the form of water present below the ground. It is called ground water. Now the question arises where does ground water come from? To enhance the thinking capabilities of students ask this question from them. After taking their views give them answer. As rain water seeps into the ground, it reaches rock strata where water cannot seep through easily. It then collects into that rock body by filling the empty spaces and cracks above that layer. It is now called the ground water. The top of that water (in the soil, sand or rocks) is called the water table. Activity: Take a beaker; keep hard stones in its bottom, than put soft soil above it and then put sand on it. Put some water above the beaker and show how water seeps into the ground through soil. Activity: Show the pictures of wells. Most of the ground water resources of Pakistan exist in the Indus plain, extending from Himalayan foot hills to Arabia Sea. Ground water is brought to the surface by means of wells, kareze. It is used for agriculture, drinking purpose and in industry. Help students in the differentiation of green and blue water: No. Green water No. Blue water 1. Water that falls as rain and is stored in the 1. Water that is sourced from rivers, lake and soil, is known as “green water” aquifers in named as “blue water”. Show the graphical distribution of water given in the book. Homework: 1. Briefly describe the occurrence of water. 2. In which forms fresh water finds on Earth? 3. Pure water is rare. Justify the statement. Conclusions: Revise the topic by showing graphical distribution of water from the pie chart. Conduct reading with correct pronunciation. Answer the questions if any, tell them about the next day lesson i.e., impurities of water. Lesson 3 Topic: 77 (5.3: Impurities of water) (5.4: Water Processing) (a) Water Treatment Teacher Resource Pack Guide Science 7 Stage – 1: Pre-treatment Teaching objectives: ⦁ Helps in the recognition of substances present in water that make the water impure. ⦁ Discuss the need of water treatment and explain stage – I of water treatment. Materials required: ⦁ Black board / white board, Chalk / Marker, Science Book – 7 CSS, Beakers, Pure water, salt, chalk powder, water treatment process figure. Key vocabulary: Dissolved impurities, suspended impurities, living matter, dissolved oxygen, hard water, screening, aeration. Introduction: Start the topic by asking questions from Lesson – I. (a) What are the effects of polluted water on plants? (b) What are the effects of polluted water on human beings? Start the topic by introducing the property of water as a good dissolving substance. That’s why, it is very difficult to find pure rain water. Rain water is the only purest form of water but when it comes in contact with atmosphere and earth’s surface, it becomes impure in many ways. Pollutants from air become its part. When water runs off on land, it dissolves impurities in it. Sunlight also supports different life forms to grow in water. All these things make rain water impure. Impurities are classified into three main categories. Dissolved Impurities Suspended Impurities Living matter All these impurities come from different sources. Lets discuss them in detail. 1. Dissolved impurities: “Those impurities which are unseen from naked eyes are called dissolved impurities.” These include: Compounds of iron, calcium and Magnesium (from soil) Gases (SO2, NO2, NO3, CO2) (from atmosphere) Fertilizer run off (coming from fields), pesticides Detergents (from house hold water) Decomposed products (from soil) The presence of these impurities is identified from their effect as: Turbidity (presence of cloudiness or haziness of a fluid) in water indicates the presence of these impurities. A layer of white solids in boiled water indicates the presence of calcium and magnesium compounds. These compounds make the water hard. “Hard water is not good for drinking and makes leather with soap”). Activity: Take pure water in a beaker. Put half water in another beaker. Add salt in it. Show the change in turbidity of water after the dissolution of salt. Also show that slats are totally soluble in water. 2. Suspended Impurities: “These impurities that do not dissolve and remain suspended in water are called suspended impurities”. These impurities may include particles of sand, clay, domestic waste, industrial waste, etc. Although, these impurities are larger but are not heavier enough to settle down if water is remained undisturbed. Activity: Crush the chalk and add its powder in water. Show the suspended water impurities to the students. 3. Living matter: When sunlight falls on impure water, it makes the water environment suitable for lower organisms to grow. These organisms may include algae, fungi, worms, bacteria, viruses, small insects and different larvae. The present of these living organisms also make the water impure. Activity: Visit some stagnant water pool which has some algae on its surface. Otherwise show the pictures. Revise the causes of impurities and tell the students. That now we will move towards the effects of impurities. Effects of Impurities: Impurities present in water deteriorate the quality of water and make it unsuitable for domestic and industrial use. 78 Teacher Resource Pack Guide Science 7 In turbid water, level of dissolved oxygen (Dissolved oxygen is the amount of gaseous oxygen dissolved in water) is very low. Such water is not suitable for aquatic life as well as for drinking. Hard water (which contains lots of minerals) makes washing difficult. It also causes digestion problems. Suspended matter intercepts the penetrating sunlight. Thus, the process of photosynthesis is prohibited. Presence of micro-organisms and chemicals make water disease causing. Activity: Give figure 5.3 in the form of work sheet for labeling. 5.4: Water Processing (Introduction): Dear students! We have already discussed that clean water is necessary for the sustenance of life. presence of impurities have different effects. Ask from students about the presence of impurities and their effects. Commonly used method of water processing is given below: Make this flow chart on board and also display figure 5.8 with the topic for complete understanding. As the chart show water treatment is divided into six stages. Stage – 1: Pre-treatment: Pre-treatment prepares the water for proper processing. Macroimpurities are removed in this stage. It accomplishes in two steps: a) Screening: In the first step, large floating debris (solids) is removed from water by passing water through large screens. These screens act as a strainer. The stage hence is called screening. b) Aeration: In the second step, fresh air is introduced into screened water. It removes unwanted gases and some microorganisms. As a result, colour, odour and taste of the water improve. This stage is known as aeration. Sometimes instead of air ozone gas is bubbled through screened water. It destroys disease causing microorganisms. Homework: 1. How does water become polluted? Conclusion: Tell the students that water processing is not complete right now. We will discuss further stages in the next lecture. Lesson 4 Topic: (Water Treatment) Teaching objectives: ⦁ Explain other stages of water treatment process. Key vocabulary: Congratulation, Sedimentation, Filtration, Chlorination, Neutralization. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Picture of water treatment process, work sheets. Introduction: The teacher must continue by revising the stage-I of the previous lecture. Ask from students: 1. Why is water processing needed? 2. What is meant by screening? 3. What is meant by Aeration? 79 Teacher Resource Pack Guide Science 7 Than draw the flow chart diagram of water treatment process, display the picture and start discussion on stage – 2 of water treatment process. Stage – 2: Coagulation: In this stage, micro-impurities are removed from pre-treated water. It also accomplishes in two steps. a) Coagulation and flocculation: Aerated water is pumped into coagulation tank. Here, tiny particle of dirt and other impurities are coagulated into large particles. It is done by adding alum. [Alum is the common name for Aluminum sulphate [Al2 (SO3)4 . 18H2O]. Alum is added with constant stirring. Alum helps these particles to stick together. This process is called coagulation which means to stick together. When these particles become larger enough to suspend in water, they are called flocs and the process is called flocculation. Teacher explains the difference between coagulation and flocculation with diagram. b) Sedimentation: The flocs particles continue to grow in size. A time approaches when these particles become heavier than water and tend to settle at the bottom of the tank. Now stirring is stopped and flocs are allowed to settle down. When the process of settling is complete, water becomes less turbid. These settled flocs are now called sludge. The process is known as sedimentation. Differentiate between flocculation and sedimentation by diagrams. Stage – 3: Filtration: Water with flocculated particles (sludge) is sent into filtration tank. Here, layers of coal, sand and gravel (small rounded stones) filter this sludge. When water passes through these layers sludge entraps in these layers and clean water comes out. After filtration water is almost clean but not ready to use. Stage – 4: Chlorination: Filtered water is still has germs. So, chlorine is added to make it sterilized. Chlorine is a very effective disinfectant. It kills all the germs present in water. Stage – 5: Neutralization: It may possible that the chemicals used to clean water i.e. alum and chlorine be added in excess amount. So, in the last stage of water treatment, lime (lime is Ca(OH)2) is added. It neutralizes the effect of all these extra chemicals. Thus, water becomes drinkable. Stage – 6: Storage and supply: Now, water is clean and ready to use. It is stored into storage tanks. From these tanks water is pumped into houses. Activity: Teacher must revise all the previous stages at this point to make them clear. Give the below work sheet to students to clarify their concept. Match the columns. A (Unwanted substances) B (Process) Floating objects Coagulation Dissolved gases + improvement taste, odor, color Sedimentation Bacteriological pollution Aeration Suspended solids Screening Excessive Fe, Ca or Hardness Chlorination Activity: Make a water treatment system in class as given in the book activity at page no. 66. b. Treatment of water to make it mineral free. There is another method to obtain clean water. It is called distillation. (Distillation is the process in which a liquid is purified by a process of heating and cooling). It is mostly used in countries where ocean water is the only source for drinking water. As we know, ocean water is too saltish to be drinkable. So, it is distilled. In Pakistan, ground water is mostly used for drinking purpose. Distillation is just used in 80 Teacher Resource Pack Guide Science 7 laboratories or in some industries to obtain mineral free water. For distillation, 1. Water is added in a flask which is fitted with thermometer. 2. Water is heated at its boiling point turn it into vapour (gaseous) state. 3. These vapours are then passed through a condenser. 4. The condenser is supplied with cold water which cools the vapours and condenses these into liquid water again. 5. This liquid is collected in a container set at the outlet of condenser and is termed as distillate. 6. The salt or other impurities remain in the flask. The water obtained in this way is absolutely pure and is called distilled water. As the distilled water is mineral free, the essential salts and mineral are added to make it drinkable. Activity: Set the distillation assembly in the laboratory and show the process of distillation to students. Homework: 1. How can the water be made salt-free? 2. Define distillation. 3. What is sludge? Conclusion: Revise all the main points from flow sheet diagram. Conduct reading by students with correct pronunciation. Answer the students question if any. Inform about the next lecture on uses of water and conservation of water. Lesson 5 Topic: (5.5: Uses of Water in Pakistan) (5.6: Water Conservation) Teaching objectives: ⦁ Explain various uses of water in Pakistan. Enhance the awareness of water conservation in students. Key vocabulary: Agriculture, industry, mechanical energy, electrical energy, conservation. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Poster showing uses of water, Water conservation methods. Uses of Water in Pakistan: First ask students the following questions because they already studied about general uses of water in previous lecture. 1. What are the uses of water in industry? 2. What are the uses of water in houses? 3. Why do plants need water? 4. Can water be used for production of electricity? In Pakistan, water is used in houses, in agriculture, in industry and as a source of electricity. Show the uses of water by displaying a poster. 1. In Homes: Ask students about the uses of water in houses and make the list on board. Drinking, working, cleaning, watering plants, washing clothes, vehicles consume 8% total water supply in homes. 2. In agriculture: Pakistan is an agricultural country. Water is mainly used for irrigation of crops. Irrigation is the watering of land to make it ready for agriculture. So, large amount of water is required for agricultural sector. It consumes 69% of total water supply. 3. In Industry: Industries in Pakistan also use water for various purposes. Steel industry used for cleaning and cooling of equipment. Paint and chemical industry used it as a solvent. Beverages industry use water as ingredient of the products. Industries use 23% of total water supply. 4. Generation of electrical energy: Water is the basic requirement in hydro-power generation. It pushes the turbines (turning wheels with blades). These turbines when move; convert the energy of moving water into mechanical energy (electricity). Hydro-power generation has a major share in industrial water requirements. Activity: Revise the above topic and give worksheet to students for filling. 81 Teacher Resource Pack Guide Science 7 Water Conservation: “Water conservation means using water carefully and wisely”. Tell the students that we have only 1% of water for all the people on Earth. We do not have its endless supply. So we not only need to save it but we must keep it clean. Ask from students about the ways to keep water clean and to conserve it. Make a list on the board. Also display the poster which shows water conservation. Also give them some advices: Turn off the tap while you are brushing your teeth. Use pan to wash fruits and vegetables. Repair any leakage in taps immediately. Water the plants in the morning and evening when temperatures are lower. It will minimize the water loss as evaporation. Avoid using shower. Use a bucket instead. Water left after washing can be used for other purposes such as watering the plants and mopping. Activity: Make groups of students and ask them to make a poster heading “Every drop counts” to aware other people about importance of a water conservation. Display the poster in school. Homework: 1. Why do we need to conserve? 2. List five different ways to conserve water? Conclusion: By concluding the lesson, revise the uses of water and ways of conservation again. Tell the students to revise full chapter and next day we will done exercise. Review Exercise A. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Choose the correct answer and fill the circle. Percentage of Earth surface which is covered by fresh water is: 25% 2.5% 97% 20% Rivers and lakes are sources of: Ocean water fresh water ground water salts water Waste material is eliminated out of the body. The substance that facilitates this movement is: Sodium chloride air water carbon dioxide Indus river provides the largest irrigation supply in Pakistan. It is termed as: salt water ground water fresh water ocean water The amount of water on Earth remains constant. The responsible phenomenon is: respiration precipitation transpiration water cycle Glaciers are frozen water. It is the form of: ground water surface water ocean water rain water The form of water with high concentration of salts is: rain water fresh water ocean water ground water The place where fresh and salt water meet is called: estuary delta aquifer none of these The term “water table” belongs to: ground water surface water ocean water fresh water Which sector is using the largest amount of fresh water? house hold agricultural industrial power generation Hardness causing mineral in water is: iron arsenic calcium copper Unwanted gases in water are removed through the process of: aeration coagulation sedimentation chlorination Water dissolves most of the impurities in it because: it is universal solvent. it is present everywhere. it is part of everything. it supports life. 82 Teacher Resource Pack Guide 14. Science 7 Which of the human activities is the direct inculcation of impurity in water? use of fertilizers construction transportation domestic discharge 15. The purpose of adding chlorine is to make water: less turbid germ free pleasant power tasteless 16. We can make the water salt-free by using the process of: water treatment filtration distillation chlorination 17. The sludge is formed in: coagulation phase sedimentation phase filtration phase chlorination phase 18. The industries that use water as raw material are: food industries nuclear reactor leather industries oil refineries 19. ‘Every drop counts’ is a slogan related to: counting drops of liquid importance of water counting drops of water importance of counting 20. A man digging the ground near a water body found that the soil was moist. As he continued digging deeper and deeper, he reached a level where all the spaces between rocks were filled with water. The upper limit of this layer is: water level water table ground water water limit B. Answer the following questions briefly. 1. What are the main uses of water in industry? Ans: Water is needed in industrial and production units. Industry requires water in many ways; as a raw material, solvent, coolant, transport agent and as energy source. 2. Briefly describe the occurrence of water. Ans: 96.5% of total global water is present in oceans and seas. 2.5% global water resources are fresh water. Fresh water resources are glaciers, ice caps, rivers, swamps, ground water and marshes. 3. How is water important for plants? Ans: 1) Water serves as a mean of transportation for dissolved nutrients and food from roots to the top most leaf. 2) Water supports plant as a skeleton by making them turgid. 3) The food preparation process-photosynthesis also requires water. 4. How can the water be made salt-free? Ans: Water is made salt-free by distillation. In this process, water is converted into vapours and then the salt-free water is collected after condensation. 5. How is water important for life? Ans: 1) Human body is comprised 70% of water. 2) Our brain receives oxygen from water only. 3) Plants prepares flood from water which is available further for living organisms. 4) Water cycle maintains the Earth’s temperature. 6. Define distillation. Ans: Distillation is the process in which a liquid is purified by a process of heating and then consecutive process of condensation. 7. What is sludge? Ans: Alum is added in water to coagulate small impurities. The coagulated particles are called flocs, when suspended. The larger flocs started to settle down. These settled flocs are called sludge. 8. In which forms fresh water finds on earth? 83 Teacher Resource Pack Guide Science 7 Ans: Fresh water is available in the form of glaciers, ice caps (68.7%), ground water (30.1%) and rivers, swamps and marshes (1.2%). 9. Pure water is rare. Justify the statement. Ans: Water is very good at dissolving substances. Rain water is the only purest form of water but when it comes in contact with air and land, it gets impure due to pollutants. Thus, pure water is rare. C. Answer these questions in detail. 1. Explain in detail the sources of water. Ans: Sources of Water: Water required for all the above mentioned purposes comes from different sources. These sources are distributed naturally in different forms and locations; on the surface, below the ground, in the oceans, etc. Water is generally categorized as follows: a. Ocean water resource b. Fresh water resource Each of these categories is a part of Earth’s water circulatory system known as water cycle or hydrological cycle. a) Ocean water resources: The largest reservoirs of water are oceans. These are generally termed as “salt water” because of high concentration of dissolved salts and minerals dissolved in it. This largest resource is divided into seven oceans throughout the Earth and accounts 97% of total water resources on Earth. Ocean water is not suitable for drinking because high amount of salts present in it make it saltish. Ocean water, however, is use for various other purposes for example, for transportation, trade, generation of electricity, tele-communication, etc. Pakistan shares ocean water boundaries in Arabian Sea on its north which is the part of Indian ocean. b) Fresh water resources: Fresh water is generally termed as “sweet water” because it has low concentration of dissolved salts and minerals. It is the water essential for human use such as drinking, agriculture, and manufacturing. Fresh water is present in very small amount; Just 2.5% of total water resource. Most of the fresh water is frozen in the form of glaciers and ice caps around North and South poles. Thus, it is not available for use. The remaining unfrozen fresh water is mainly found as ground water and as running water above the ground. This running fresh water is available in the forms of rivers, lakes, swamps, etc. Fresh water sources in Pakistan mainly depends upon Indus water system and its tributaries i.e. Jhelum, Chenab, Beas, Sutlej, Ravi. Ground water resources: The largest useable proportion of fresh water is in the form of water present below the ground. It is called ground water. Where does ground water come from? As rain water seeps into the ground, it reaches rock strata where water cannot seep through easily. It then collects in that rock body by filling the empty spaces and cracks above that layer. It is now called ground water. The top of that water (in the soil, sand, or rocks) is called the water table. Most of the ground water resources of Pakistan exist in the Indus plain, extending from Himalayan foothills to Arabian Sea. Ground water is brought to the surface by means of wells, kareze. It is used for agriculture, drinking purpose and in industry. A graphical distribution of water is clear in the chart below: 2. How can we treat water on large scale? Ans: Water treatment: In this process, water is made drinkable by passing it through six different stages. These stages are discussed below: 84 Teacher Resource Pack Guide Science 7 Stage – 1: Pre-treatment: Pre-treatment prepares the water for proper processing. Macroimpurities are removed in this stage. It accomplishes in two steps: a) Screening: In the first step, large floating debris (solids) is removed from water by passing water through large screens. These screens act as a strainer. The stage, hence, is called screening. b) Aeration: In the second step, fresh air is introduced into screened water. It removes unwanted gases and some microorganisms. As a result, colour, odour and taste of the water improve. This stage is known as aeration. Sometimes, instead of air, Ozone gas is bubbled through screened water. It destroys disease causing microorganisms. Stage – 2: Coagulation: In this stage, micro-impurities are removed from pre-treated water. It also accomplishes in two steps: a) Coagulation and flocculation: Aerated water is pumped into coagulation tank. Here, tiny particles of dirt and other impurities are coagulated into larger particles. It is done by adding alum (aluminum sulphate: [Al2 (SO3)4.18H2O] with constant stirring. Alum helps these particles stick together. When these particles become larger enough to suspend in water, they are called flocs. The process is called coagulation and flocculation. b) Sedimentation: The flocs particles continue to grow in size. A time approaches when these particles become heavier than water and tend to settle at the bottom of the tank. Now, stirring is stopped and flocs are allowed to settle down. When the process of settling is complete, water becomes less turbid. These settled flocs are now called sludge. The process is known as sedimentation. Stage – 3: Filtration: Water with flocculated particles (sludge) is sent into filtration tank. Here, layers of coal, sand and gravel filter this sludge. When water passes through these layers, sludge entraps in these layers and clean water comes out. After filtration, water is almost clean but not ready to use. Stage – 4: Chlorination: Filtered water is still has germs. So, chlorine is added to make it sterilized. Chlorine is a very effective disinfectant. It kills all the germs present in water. Stage – 5: Neutralization: It may possible that the chemicals we used to clean water i.e. alum and chlorine be added in excess amount. So, in the last stage of water treatment, lime is added. It neutralizes the effect of all these extra chemicals. Thus, water becomes drinkable. Stage – 6: Storage and supply: Now, water is clean and ready to use. It is stored into storage tanks. From these tanks, water is pumped into houses. 3. Draw a flow sheet of water treatment process. Ans: Water treatment process: 85 Teacher Resource Pack Guide Science 7 4. How does water become polluted? Ans: Impurities of Water: Water is very good at dissolving substances. Thus, it is very unusual to find really pure water. Rain water is the only purest form of water. When it comes in contact with atmosphere and with Earth's surface, it becomes impure in many ways. In air, some of the pollutants of air and land become the part of rain water. Many of the compounds generally dissolve in rains when water it runs off along the surface. Moreover, sunlight supports a range of life form to grow in water when sunlight falls on it. All these things make rain water impure. These impurities may be classified into three categories: 1) Dissolved impurities 2) Suspended impurities 3) Living matter All these impurities come from different sources. Here below, these are discussed in detail. 1) Dissolved impurities: Dissolved impurities cannot be seen with naked eye. These include compounds of Iron, Calcium and Magnesium, gases (SO2, NO2, NO, CO2), fertilizer run off, pesticides, detergents, decomposed products, etc. The presence of these impurities is identified from their effect as: Turbidity in water indicates the presence of these impurities. A layer of white solids in boiled water indicates the presence of calcium and magnesium compounds. These compounds make the water 'hard'. 2) Suspended impurities: Impurities that do not dissolve and remain suspended in water are called suspended impurities. These impurities may include particles of sand, clay, domestic waste, industrial waste, etc. Although, these impurities are larger but are not heavier enough to settle down if water is remained undisturbed. 3) Living matter: When sunlight falls on impure water, it makes the water environment suitable for lower organisms to grow. These organisms may include algae, fungi, worms, bacteria, viruses, small insects and different larvae. The presence of these living organisms also makes the water impure. 5. Why do we need to conserve water? Ans: Water conservation: Water conservation means using water carefully and wisely. Our water resources are limited. It means that we do not have endless supply of water. Only 1% of water is available for all the people on Earth. So, we must not only conserve our water but must keep it clean as well. 6. List five different ways to conserve water. Ans: We can save water by adopting following ways: Turn off the tap while you are brushing your teeth. Use pan to wash fruits and vegetables. Repair any leakage in taps immediately. Water the plants in the morning and evening when temperatures are lower. It will minimize the water loss as evaporation. Avoid using shower. Use a bucket instead. Water left after washing can be used for other purposes such as watering the plants and mopping. Unit # 6 STRUCTURE OF AN ATOM Lesson 1 Topic: (6.1: Structure of an atom) Teaching objectives: ⦁ Explain the structure of atom in detail. Key vocabulary: Election, Proton, Neutron, Atom. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Picture of atom with particles, work sheet. Introduction: Ask from students about the atom. What they know about atom from their previous classes. Write their information in the form of point. 86 Teacher Resource Pack Guide Science 7 They already know that matter is made up of small particles called atoms. Tell them about the history of the discovery of atoms. Greek philosopher Democritus (600-400 BC) gave the concept of atoms. According to him: 1. Atoms are the smallest particles of matter. 2. They are fundamental units. 3. They are non-divisible. For example, take a chalk and break it in smallest possible parts. The smallest part of chalk which is further non-divisible in known as atom. From here the Greeks derived the name ‘atamio’ which mean ‘uncut-able’ or “non-divisible”. Later studies proved that atom is not the smallest particle. It contains many sub-atomic particles i.e. electrons, protons and neutrons. Each particle has its own features. Structure of an Atom: For understanding the structure of an atom, two aspects must be considered in mind i.e. (1) Sub-atomic particles. (2) Arrangement of sub-atomic particles within an atom. Activity: Teacher must display the structure of atom on chart or on multimedia. If possible, arrange a model of an atom. We will discuss three sub-atomic particles i.e. electron, neutron and protons. Electron: Electron is the smallest and first discovered particle. The discovery of electron made the atom divisible. It was discovered by J.J. Thomson in 1897. These electrons revolve around the nucleus in specific paths which are known as shells. Mass and size of an atom are extremely small. Its mass is 9.11×10-31 kg and it carries negative charge. Electron of an atom takes part in a chemical reaction. Proton: Rutherford discovered the nucleus of atom. Proton is found in the nucleus of the atom. It was also discovered by Rutherford in 1920. It carries positive charge. Mass of proton is 1.67×10 27 kg. Mass of proton is 1837 times greater than that of an electron. It is larger in size than electron. Numbers of protons are fixed for an atom. Neutron: Neutron also resides in the nucleus of an atom. It was discovered by James Chadwick in 1932. Its mass is same as that of proton 1.63×10-27. It possesses no charge. So, it is electrically neutral. Neutron is almost or same size to that of proton. Although neutrons have no charge yet they play a great role in mass of an atom. Activity: Give students work sheets which contain structure of an atom. Tell them to label it. Atoms are electrically neutral: Students must be kept in mind that atoms have different charged particles but there overall charge is zero or neutral. How’s it is possible? The reason is atom contains equal number of positive charged particles (protons) and negative charged particles (electrons). They cancel out each other’s effect and make atom neutral specie. Lets take an example of carbon atom. Carbon contains 6 electrons, 6 protons and 6 neutrons, 6 electrons contain negative charge and 6 protons contain positive charge. They can cancel the effect of each other. –6 +6 0 Homework: 1. Describe the contribution of Rutherford in development of structure of an atom? 2. Is an atom really indivisible? If not, How? Discussion: At the end of the topic discuss some other examples related to the electrical neutrality of an atom. Conclusion: Conclude the topic by revising all the important points. Tell them about the next topic atomic number and mass number. Activity: 1. Calculate number of protons, if number of electrons are 11. Is this atom neutral? 2. An atom is neutral. It has 7 protons. How many electrons it contain? Lesson 2 Topic: Teaching objectives: 87 (6.2: Atomic number and Mass number) ⦁ Describe atomic number and mass number. Teacher Resource Pack Guide Science 7 ⦁ Differentiate between atomic number and mass number. ⦁ Calculate the atomic number and mass number. Key vocabulary: Atomic number, Mass number, Proton number. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Worksheets, chart of elements containing atomic number, mass No. 4 other details. Introduction: Start lecture from the previous topic and ask following questions. 1. How many sub-atomic particles atoms contain? 2. How many particles are present in nucleus? 3. Why is atom neutral? 4. If atom has 4 protons than how many electrons it contains? Tell the students that there are more than 100 elements known. Each element is different from other because of the difference in number of protons and neutrons. These particles give elements (atoms) different properties. Two of these properties are atomic number and mass number which we discuss in detail. Atomic number: Every element has fix number of protons. “The number of protons is termed as its atomic number. It is represented by Z”. Consider following examples: 1. Hydrogen (H) has one proton only. So, its atomic number is 1. In this way, it is the smallest element of the periodic table. 2. Carbon (C) has six protons. Its atomic number is 6. 3. Sodium has eleven protons. Its atomic number is 11. Number of protons = Atomic number Mass Number: We already know that mass of atom resides in its nucleus. Nucleus contains protons and neutrons. So, “mass number of an atom is total number of protons and neutrons present in an atom. It is represented by “A”. Electrons do not usually weigh much. So, mass number is calculated by adding protons and neutrons. Consider following examples: 1. Hydrogen (H) has one proton only. It has no proton. So, its mass number is 1. 2. Carbon (C) has six protons and six neutrons. Its mass number is 12. 3. Sodium has 11 protons and twelve neutrons. So, its mass number is 23. Mass number = Number of protons + Number of Neutrons Teacher Note: Help the students in the learning of element name and their symbols up to 18 elements. Activity: Solve the work sheet in class. 1. Number of Neutrons = 9 Number of protons = 9 Mass Number = ? Atomic Number = ? 2. Number of Neutrons = 18 Number of protons = 17 Mass Number = ? Atomic Number = ? 3. An element has 5 numbers of protons and 6 numbers of neutrons. Find out its atomic number and mass number. 4. Oxygen has 8 numbers of protons. Its mass number is 16. Find out its atomic number and number of neutrons. 5. The mass number of fluorine is 19. Its atomic number is 9. Calculate its number of protons and number of neutrons. Homework: 1. What is the atomic number of the atom? 2. An element has 17 electrons and 18 neutrons. Calculate its atomic number and mass number. 3. Differentiate between atomic number and mass number? Conclusion: After knowing about the sub-atomic particles and their properties, now the questions arises how these particles arrange themselves in the atom. We will study it in the next lecture. 88 Teacher Resource Pack Guide Science 7 Lesson 3 Topic: (6.3: Electronic Configuration) Teaching objectives: ⦁ Learn about the structure and model of atom. ⦁ Explain atom with electronic distribution and discuss concept of electronic configuration. ⦁ Know the electronic distribution and structure of first eighteen elements. Key vocabulary: Electronic configuration, shells. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Model / Chart display pictures of elements with electronic distribution and structure. Introduction Atom has two parts. It has nucleus in its center which contains proton and neutrons. It has electron which are moving outside the nucleus in specific paths. These orbits or paths are called shells or energy levels. There cells are at specific distance from the nucleus. The structure of atom resembles to our solar system in which sun acts as nucleus and electrons are revolving around it like planets. Shells: The orbits or paths in which electrons move around the nucleus are called shells or energy levels. These shells are given the specific names as K, L, M, N, O, P and Q. The shell closest to nucleus is labeled as K, the next shell is labeled as L, and so on. The arrangement of electrons in different shells is known as electronic configuration. Pattern of filling Consider the Fig 6.3 and follow the discussion. Shell closest to nucleus which is L-shell has lowest energy. L-shell has more energy than k-shell but less energy than M-shell. M-shell has more energy than L-shell but less energy than N-shell. The pattern of increasing energy is: K-shell < L-shell < M-shell < N-Shell ….. Electrons must fill the lowest energy shell first. So, first electrons fill kshell, than L-shell, than M and so on. The filling of electron is also dependent. Every shell can accommodate maximum number of electrons, as given below: K-shell can accommodate only two electrons. L-shell can accommodate only 8 electrons. M-shell can accommodate 18 electrons and so on. Now take an example of sodium (Na). it has 11 electrons, 11 protons and 12 neutrons. Sodium has 11 electrons revolving around its nucleus. K-shell contains 2 electrons. L-shell contains 8 electrons. M-shell contain 1 electron. Shells can accommodate fewer electrons than their maximum limit but they cannot accommodate more electrons than their maximum limit. Point to remember that number of protons is equal to number of electrons. If an element has atomic number 5 it means it has 5 electrons in normal state. 89 Teacher Resource Pack Guide Science 7 Activity Solve the worksheet. 1. Label the diagram below and give electrons number. Boron 5B 2. Fill the electrons in shell according to given atomic number. 12Mg Also write number of electrons below: K-shell __________, L-shell __________, M-shell__________ 3. Draw atomic structure of Neon (10N) Importance of electronic distribution: The number and arrangement of electrons in an atom is important because it controls the chemical properties of the atom. Valence Shell: Valence shell is the outermost shell of an atom which mostly takes part in the chemical reaction. Elements tend to fill their valence shells. When the shell is filled, element is happy and stable. If the valence shell is filled with 2-electrons it becomes happy under duplet rule. When it becomes stable with 8-electrons, it happens under octet rule. For example the valence shell of oxygen contains 6 electrons. Valence shell of sodium has 1 electron and chlorine has 7 electrons. Valence shells are mostly incomplete. But few elements have complete valence shells like Helium has 2 electrons in valence shell. Neon has 8 electrons in its valence shell. They are considered as stable. Homework: 1. Solve question D from page 77. 2. Define valence electrons. How are they important? Conclusion: Conclude the chapter by revising main points. Inform the students that we will revise the chapter and complete the test exercise 1. Test Exercise – 1 A. 1. 2. 3. 4. 5. 6. 7. Choose the correct answer and fill the circle. The building block of matter is atom. The reason for this concept was that atom considered as: smallest particle divisible particle non-divisible particle only available particle The atom was given the status of being non-divisible by: Aristotle Democritus Plato John Dalton How many sub-atomic particles are present in an atom? two three four five Identify the sub-atomic particle with negative charge. neutron proton electron quark The charge on neutron is: positive negative partial positive no charge An element has 79 protons, 79 electrons and 118 neutrons. Its mass number is: 158 197 355 39 Suppose an atom has a mass number 15. The atom contains 8 protons. How many neutrons does it has? 7 8 9 15 90 Teacher Resource Pack Guide Science 7 8. The shell that can accommodate only 2 electrons is: K L M N B. Answer the following questions briefly. 1. Describe the contributions of Rutherford in development of structure of an atom. Ans: Rutherford discovered the nucleus of an atom and in 1920 he discovered the protons in nucleus. 2. Is an atom really non-divisible? If not, How? Ans: Atom is divisible because it contains sub-atomic practices. It can easily lose its electrons during chemical reaction. 3. What are energy levels? Ans: Electrons move in circular orbits around the nucleus. These orbits or paths are called shells or energy levels. 4. When does an electron release or absorb energy? Ans: Electrons move around the nucleus in specific orbits. Each orbit has specific energy. When electron jump from lower energy orbit to higher energy orbit it absorbs energy. When electrons go from higher energy orbit to lower energy, it releases energy. 5. An element has 17 electrons and 18 neutrons. Calculate its atomic number and mass number. Ans: No. of electrons is equal to No. of protons. So, atomic number is 17. Sum of protons and neutrons = 17 + 18 Mass number = 35 C. The following atomic model contains one orbiting electron and a nucleus of one proton. a) What is the atomic number of the atom? Ans: No. of protons = No. of electrons So, Atomic number is 1. b) Identify the element. Ans: It is Hydrogen. D. Circle valence electrons only. How many valence electrons does each atom has? F has 7 valence electrons. Cl has 7 valence electrons. Br has 7 valence electrons. Iodine has 7 valence electrons. E. Draw the structures of following elements. Silicon Potassium Si 14 19K 91 Teacher Resource Pack Guide Sulphur Science 7 Boron 16S 5B Lesson 4 Topic: (6.4: Valency and Ions) (6.4.1: Valency) Teaching objectives: ⦁ Discuss concept of valency. ⦁ Discuss why atoms gain or loose electrons with examples. Key vocabulary: Vlency, valence shells. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Display charts of atomic models, worksheets. Introduction: Students you have already studied about atomic shells and valence shell. When atomic shell of an atom is full, it becomes stable. Let’s study the examples Helium 2He. Helium (2He): 2 electrons 2He – 1 filled shell Neon (10Ne): 10 electrons 2 filled shells 10Ne – Ask from students how many electrons needed to fill the shells? 2 – electrons in case of duplet rule. 8 – electrons in case of octet rule. Most of the cases electrons have unfilled atomic shells. For example: Sodium (11Na): Oxygen (8O): 11 electrons 8 electrons 2 filled shells – K, L 1 shell filled – K rd 1 electron in 3 shell, M 6 electrons in 2nd shell – L 92 Teacher Resource Pack Guide Science 7 Now, in order to be stable, they need to lose or gain electrons in outermost shells. They have two possibilities. 1. They can get electrons to fill their shells. 2. They can lose electrons and have completed inner shells. It is easy for 11Na to lose 1 electron from M shell rather than to gain 7 electrons. So, it loses its one electron and L shell becomes outermost (filled) shell. In case of oxygen, L-shell contains 6 electrons. It is difficult for oxygen to lose all six electrons to achieve stability. So, it gains two electrons and completed its L-shell. Activity: Make electronic structures of Magnesium (12Mg) and chlorine (17Cl) gain or loose on board. Ask show how much electrons they are required to fill their valence shells. Questions of Activity: 1. How many total electrons a magnesium atom contain? 2. How many shells are complete in magnesium? 3. Which shell is incomplete in magnesium? 4. How much electron Mg gains or loses to get stabilizes? 5. Write total number of electrons in chlorine? 6. How many shells are complete in chlorine? Write their names? 7. Which shell is incomplete? How many electrons it is need to complete its shell? Magnesium loses 2 electrons to become stable and chlorine gain 1 electron to become stable. In the light of above discussion valency is defined as: “The number of electrons an atom gains, loose or shares to make it stable (outer shell complete), is called its valency”. Keep in mind that while describing the valency; positive and negative charges must be shown with it. Positive sign represents loss of electron and negative sign represent gain of electron. Like Sodium-11 lose 1 electron and its valency is +1. Chlorine gains 1 electron so it its valency is -1. Valency and its signs are written as superscript to the right side of the element symbols. Like Na+ for sodium, Cl- for chlorine, O2- for oxygen and Mg2+ for Magnesium. Activity: Give them a worksheet to draw electronic structures of Calcium (20Ca) and Sulphur (16S). Also write their valencies with signs. Homework: 1. Hydrogen has one electron in its outermost shell. How many electrons hydrogen needed to complete duplet? Write its valency with sign. 2. Aluminium (Al-17) is a light metal. Draw its atomic structure and describe its valency with sign. Conclusion: The teacher should revise the valency rules from board. Tell them today we have just learn about valency and in the next lecture, we will study ions. Both topics are related with each other and you must know about valency to develop the concept of ions. Lesson 5 Topic: (6.4.2: Ion) Teaching objectives: ⦁ Explain the relationship between valency and ion. ⦁ Describe the formation of ions. Key vocabulary: Ion, valency, Cation, Anion. 93 Teacher Resource Pack Guide Science 7 Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Chart of Ion formation, worksheet. Introduction: Valency and ions are closely related. The number of gained or lost electrons is called valency and when an atom receives or gives up electrons, it becomes an ion. So, “ions are the atoms with extra electrons or missing electrons”, as compared to neutral atom. “A neutral atom is an atom having number of electrons equal to its atom number”. Let’s answer few questions. 1. Which charge come on atom when it lose electron? 2. Which charge come on atom when it gain electron? Let consider an example of ion formation in sodium chloride (NaCl). As shown in above figure, ions are of two types: 1. When an atom releases electron(s), it becomes a cation. A cation carries positive charge. Examples are sodium (Na+), Potassium (K+), Calcium (Ca2+) etc. Usually metal atoms release electrons. 2. When an atom gains electron(s) it becomes an anion. It carries negative charge. Non-metal atoms gain electrons. The name of an anion is changed to and “ide” while cation is named as whole. Common anions are Fluoride (F-), Chloride (Cl-), Bromide (Br-), Oxygen (O2-) etc. Activity: Ask questions from the following diagram of ion formation. Draw the diagram on board. 94 Teacher Resource Pack Guide Science 7 1. 2. 3. 5. 6. 7. How many total electrons calcium atom has in its shells? How many total electrons fluorine has in its shells? How many electrons calcium lose? 4. How many electrons fluorine gain? Write valency of Calcium and Fluorine ions? How many electrons calcium ion has in its shells? How many electrons are present in fluorine ions? When an atom receives or gives electron(s) to another atom, it make bond with that atom. The two or more bonded atoms are known as ionic compound. For example, chlorine atom receives its missing electron from sodium atom, thus, makes bond with it. As a result, a compound NaCl is formed. Activity: Draw and describe bond formation in following compounds. Write name of compound, no. of electrons before and after formation of ions. Also mention cations and anions. a) KF b) LiH Homework: Write down the ions formed from these elements. Write down their formulae showing the charge they carry. Ca Br Na S I O K N Al Mg Ba Sr Li Cl F Conclusion: The teacher should revise all the main points from board regarding ion formation and tell them they will study isotopes in the next lecture. Lesson 6 Topic: (6.5: Isotopes) Teaching objectives: ⦁ Introduce the concept of Isotopes. ⦁ Discuss different isotopes of elements. ⦁ Explain the uses of isotopes. Key vocabulary: Isotopes, Protium, Deuterium, Tritium. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Chart of isotopes of hydrogen and carbon, worksheet. Introduction: Ask students what happened when we add extra neutron in an atom of hydrogen? They will answer that the mass number of hydrogen increases due to the addition of neutron. Tell them this is called isotope. Isotopes are still the same elements just like ions which remain same after missed electron(s) or by having extra electron(s). The only difference arises in their mass, because neutrons correspond to mass. When number of neutron changes, mass number also changes. So, an isotope is defined as: “The elements having same atomic number but different mass number are called isotopes”. Consider following examples for the clear idea. Isotopes of Hydrogen: Hydrogen has three isotopes. The isotopes have their specific names. The common hydrogen that has zero neutrons is called protium. Hydrogen having one neutron is called deuterium while hydrogen with three neutrons is called tritium. 95 Teacher Resource Pack Guide Science 7 Isotopes of Carbon: Carbon also has three isotopes. They are not given any specific name. There are carbon-12, carbon-13 and carbon-14 isotopes with mass number 12, 13 and 14 respectively. Some elements have two isotopes, some have three and few elements have more than three isotopes. Activity Solve the worksheet. 1. Write number of protons and neutrons in the following isotopes. Proton Neutron Ans: N14 : Number of protons: 7 Number of neutrons: 7 N15 : Number of protons: 7 Number of neutrons: 8 2. Find out number of protons and neutrons in the isotopes of Sodium. 23 24 11 Na 11 Na 23 11 Na Mass numbers = 23 Atomic number = 11 As atomic number = No. of protons So, 24 11 Na 11 = 11 Number of neutrons = Mass number – Atomic number 23 – 11 = 12 Mass numbers = 24 Atomic number = 11 As atomic number = No. of protons So, 3. 11 = 11 Number of neutrons = Mass number – Atomic number 24 – 11 = 13 Fine number of neutrons in the isotopes of oxygen. 16 17 18 8 O 8 O 8 O 16 8 O 96 Atomic numbers = 8 Mass number = 16 Number of neutrons = Mass number – Atomic number Teacher Resource Pack Guide Science 7 16 – 8 = 8 Atomic numbers = 8 O Mass number = 17 Number of neutrons = Mass number – Atomic number 17 – 8 = 9 18 Atomic numbers = 8 8O Mass number = 18 Number of neutrons = Mass number – Atomic number 18 – 8 = 10 Uses of Isotopes: Isotopes can be useful in different industries, such as food, agriculture, archaeology and medicine. Some of their uses are given below: Medicine: In the field of medicine isotopes (radioactive) are used for radiation therapy. It locates tumors in brain. Some other uses are given in the chart: Isotope Application in medicine Cobalt-60 Used in radiation therapy to prevent cancer Iodine-131 Locate brain tumors, cure goiter Sodium-24 Study blood circulation Thallium-201 Identify damage in heart tissues Agriculture: In agriculture, isotopes help in various fields as follow: An isotope of phosphorus (P-32) is used in phosphorus containing fertilizers. It helps to detect the metabolism of phosphorus in plants. An isotope of carbon (C-14) is used to study the passage of carbon in plants during photosynthesis. Activity: Tell the students that human body also contains isotopes of potassium-40 and carbon 14. Tell them to find out no. of protons & neutrons in K-40 and C-14. Homework: 1. Define isotopes. 2. What are radioactive isotopes? Conclusion: The teacher should revise all the main points about isotopes. Tell them tomorrow we will study about molecules and chemical formula. 17 8 Lesson 7 Topic: (Molecules and chemical formula) Teaching objectives: ⦁ Discuss the concept of molecule. ⦁ Differentiate between homo-atomic and hetero-atomic molecule. ⦁ Explain how to write chemical formula of molecules. ⦁ Explain how to write chemical formula of organic compounds. Key vocabulary: Isotopes, Molecules, compounds, Ionic compounds. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Pictures of molecules, worksheets. Introduction: “A molecule is a chemical combination of two or more atoms of same or different types”. Molecule exist independently. All compounds are molecules but all molecules are not compounds. Ask about the difference in atom and element? Tell them same difference exist between molecule and compound. Type of molecules: There are two types of molecules. If combining atoms are of some type, the molecule formed is homo-atomic. For example, oxygen in which two oxygen atoms combine making oxygen molecule (O2). Similarly, hydrogen (H2), fluorine (F2) and iodine (I2) are homo-atomic molecules. Combining atoms may be of two or more different types forming hetero-atomic molecules. For examples, Water (H2O) is a hetero-atomic molecule containing two hydrogen and 97 Teacher Resource Pack Guide Science 7 one oxygen. Sugar (C6H12O6) hetero-atomic containing 6 carbon, 12 hydrogen and 6 oxygen. Sand (SiO2) is also hetero-atomic molecules containing one silicon and two oxygen atoms. Activity: Differentiate between homo-atomic and hetero-atomic molecules. Write in separate columns. Br2, H2, SiO2, H2O, O2, CO2, Cl2, HCl, HF, I2 Chemical formula of molecules: Elements are represented with their symbols, as you all know that. Molecules need chemical formula for their symbolic representation. The constituents of a molecule and their number can be shown through a chemical formula. A chemical formula is the simplest but comprehensive notation that tells which elements and how many atoms of each element make up a molecule. In a chemical formula, elements making up a molecule are denoted by their symbols. Whereas, number of each element is written as subscripts beside each atom. Consider an example of methane. Methane has one carbon atom and four hydrogen atoms. The chemical formula is CH4. Likewise sugar has chemical formula C6H12O6. In the same way nitrogen has N2, Iron oxide has Fe2O3, Ammonia has NH3, Sulphuric acid has H2SO4 etc. Activity: Write number of atoms in following molecules. C12H22O11, NH3, H2SO4, PCl5, I2, Br2, HCl, CO2, H3PO4, SiO2. Chemical formula for Ionic Compounds: First tell the students about the difference in molecules and compounds. Every combination of atoms is a molecule. Atoms in the molecules or compounds are joined with each other through chemical bonds. Ionic bond is a type of chemical bond which formed between cation and anion and form ionic compounds. To write formula of an ionic compound following steps are used: Chemical formula for ionic compounds: When a cation (metal element) chemically combines with an anion (non-metal), a compound is formed. It is an ionic compound. To write the formula of an ionic compound, following steps are used: Step–1: Identify the cation and anion. Write the symbol of cation first and the anion second. Example 1: In compound magnesium chloride (MgCl2), magnesium is a cation and chloride is an anion as: Mg Cl Example 2: In compound aluminum chloride (AlCl3), aluminum is cation and chloride is an anion as: Al Cl Example 3: In compound iron oxide (Fe2O3), Iron is a cation and oxide is an anion as: Fe O. Step–2: Identify the valency of anion and cation. Put the valency number of each ion with its charge on its top right side. Example 1: Mg2+ Cl1Example 2: Al3+ Cl1Example 3: Fe3+ O2Step–3: Crisscross method for writing formula is used to complete the formula. In this method, interchange the valency number of both ions and write them on lower right side of each ion. Omit the +ve and –ve signs. Reduce the ratio by a common factor if possible. Activity:Make compounds and write chemical formula from the given list of anions and cations. 98 Teacher Resource Pack Guide Science 7 No. Cations (+) / Anions (-) Chloride (Cl-) Chloride (O2-) Iodide (I-) Sulfide (S)21. Sodium (Na+) 2. Potassium (K+) 3. Magnesium (Mg2+) 4. Calcium (Ca2+) 5. Copper (Cu2+) 6. Iron (Fe2+) 7. Iron (Fe3+) 8. Silver (Ag1+) Homework: Make the ionic structures of following compounds and answer the questions. (a) AlP (b) NaH (i) Write the name of each compound. (ii) Guess the valency of each element in each compound. (iii) Mention the ions formed (anions and cations) in each compound. Conclusion: Revise all the main points from board. Tell them we will study law of constant composition in next lecture and solve the test exercise 2. Lesson 8 Topic: (6.7: Law of Constant composition) Teaching objectives: ⦁ Discuss the law of constant composition. ⦁ Explain its importance in writing chemical formula. Key vocabulary: Constant composition. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7. Introduction: The law of constant composition states that: “Composition of a compound is always the same”. Explanation: It means that a compound always contains the same constituents in the same proportion by weight. The factors such as formation method, amount of compound and state of compound do not affect the composition. Examples: For example, whenever we talk about water, whether it is in liquid state, frozen or in gaseous state, it always has two atoms of hydrogen and one atom of oxygen H2O. Moreover, whatever the sources of water like water from river, ocean, well, tube well even tap water all has some chemical composition. If you add one extra oxygen in H2O it becomes H2O2 which is hydrogen peroxide. It possesses totally different properties than water. Similarly, CO2 is a life gas for plants. It possesses one carbon and two oxygen atoms. If you reduce it to one oxygen atom it becomes (CO) which is highly poisonous and can cause death if inhale even a minute. Activity: Write one example of law of constant composition. Homework: Explain the law of constant composition. Conclusion: Revise all the main points from board. Inform the students we will do test exercise – 2 after this topic. In next lecture we will revise the chapter – 6 and then solve the exercise. Test Exercise – 2 A. 1. 2. Choose the correct answer and fill the circle. Combining power (valency) of Chlorine is: 2 1 4 A charged atom or molecule is known as: ion electron isotope 99 3 compound Teacher Resource Pack Guide 3. 4. 5. 6. 7. 8. 9. B. 1. Ans: 2. Ans: 3. Ans: 4. Ans: Science 7 If number of electrons in an atom is less than number of protons, the charge on the atom will be: negative positive zero double negative How many neutrons are found in C-14? 6 7 8 9 The isotope of hydrogen responsible for making water heavy is: protium deuterium tritium none of these The isotope that is used to study blood circulation is: coblat-60 sodium-24 carbon-14 phosphorus-32 In carbon, the number of valence electrons is: 3 4 7 8 To complete the octet of an atom, the required electrons are: 2 8 18 32 Radioactive isotopes are unstable because: they are weak their valence shell is incomplete they have heavy nucleus they have high energy Answer the following questions briefly. Define valency. The number of electrons an atom gains, lose or share to make itself stable (outer shell complete) is called its valency. How can the valencies of an atom be determined from periodic table? The valency of an atom can be found from periodic table. The vertical column of periodic table are called groups. Group number of an atom is its valency number as well. What is octet rule? Elements tend to fill their valence shell. If valence shell is filled with 8-electrons, it is known as octet rule. Define isotopes. The elements having same atomic number but different mass number are called isotopes. Review Exercise A. 1. 2. 3. 4. 5. Choose the correct answer and fill the circle. The sub-atomic particles found in the nucleus are: electron, proton electron, neutron proton, neutron only proton Electrons revolve around nucleus in fixed paths. These paths are called: tracks shells route channel An atom posses both positively and negatively charged particles. But overall, atom is a neutral particle. The reason is: oppositely charged particles are equal in number oppositely charged particles are same in size oppositely charged particles have equal weights neutral particles are greater in number The letter “Z” in chemistry represents: atomic number mass number valency valence electronic shell An element has 19 electrons. Arrange these electrons in K, L, M and N shells: 2,8,9 2,8,8,1 9,8,1 2,8,4,4 100 Teacher Resource Pack Guide Science 7 6. The combining power of an atom is called: chemical bond valency intermolecular force force of attraction 7. Which of the following species carries negative charge? proton cation anion neutron 8. The isotopes of carbon elements are: 2 3 4 5 9. Uranium-235 is an important radioactive isotope. It is mainly used in/to: nuclear power generation study blood circulation fertilizers prevent cancer 10. The chemical formula of calcium chloride is: CaCl CaCl2 Ca2Cl Ca2Cl2 B. Write down the ions formed from these elements. Write down their formulae showing the charge they carry. Element Ion Element Ion Ca Ca2+ Ba Ba2+ S S2Cl ClK K+ Na Na+ 2+ Mg Mg O O2Li Li+ Al Al3+ Br Br Sr Sr2+ I IF F3N N C. Answer the following questions briefly. 1. Differentiate between atomic number and mass number. Ans: Differentiate between atomic number and mass number. No. Atomic Number No. Mass Number i. The number of protons in an element is i. The total number of protons and neutrons termed as its atomic number. present is an atom is termed as mass number. ii. It is represented by Z. ii. It is represented by A. iii. Atomic number of each element is always iii. Mass number is changed in case of isotopes fixed. of elements. 2. Draw and label the structure of an atom. Ans: 3. Ans: 4. Ans: 5. Define the electronic configuration. “The arrangement of electrons in different shells is known as electronic configuration”. What is the number of electrons in an atom whose atomic number is 14? Number of electrons is equal to number of protons and atomic number shows number of protons, so number of electrons is also 14. What is an ion? 101 Teacher Resource Pack Guide Science 7 Ans: “Ions are the atoms with extra electrons or missing electrons”. These are charged species. For Example: Na ion is Na+ and Cl ion is Cl-. 6. Define valance electrons. How are they important? Ans: Electrons present in valence shell are known as valence electrons. Valence shell are mostly outermost and incomplete shells. Valence electrons tell us about the valency of an element. 7. Draw and label three isotopes of hydrogen atom. Ans: 8. What are radioactive isotopes? Ans: Some isotopes are unstable. They emit radiations to become stable. Such isotopes are called radioactive isotopes. 9. How can the goiter be cured? Ans: Goiter can be cured by the radiation therapy of radioisotope of Iodine – 131. D. Answer the questions in detail. 1. Compare all the three sub-atomic particles. Ans: Electron Proton Neutron -27 -27 -31 1.67×10 kg 1.67×10 kg Mass 9.11×10 kg Negative Positive Neutral Charge J.J. Thomson Rutherford James Chadwick Discovery Outside the nucleus Inside the nucleus Inside the nucleus Location in atom Not involved Not involved Role in chemical reactions Involves in reaction 2. Describe the structure of an atom in terms of its particle. Ans: Structure of an atom: The structure of an atom is best explained by explaining two aspects i.e. (1) sub-atomic particles (2) arrangements of these particles within an atom. Electron: Electron is the smallest and the first discovered particle. The discovery of electron made the atom divisible. It was discovered by J.J. Thomson in 1897. These electrons revolve around nucleus in specific paths (shells). Mass and size of an electron are extremely small. Electrons of an atom take part in a chemical reaction. Proton: Proton is found in the nucleus of the atom. It was discovered by Rutherford in 1920. It carries positive charge. Mass of proton is 1837 times greater than that of an electron. It is larger in size than electron. Number of protons is fixed for an atom. Number of electrons is equal to number of protons. Neutron: Neutron also resides in the nucleus of an atom. It was discovered by James Chadwick in 1932. It possesses no charge. So, it is electrically neutral. Neutron is almost same in mass and size to that of proton. Although, neutrons have no charge yet they play a great role in mass of an atom. 3. How do ions make ionic compounds? Ans: Valency and ions are closely related. The number of gained or lost electrons is called valency and when an atom receives or gives up electrons, it becomes an ion. So, “ions are the atoms with extra electrons or missing electrons”, As compared to neutral atom. Let us study the Sodium atom again. As valency of sodium is ‘1+’ (it loses one electron), the number of protons get increase than electrons. Now, Sodium has become an ion. As number of protons (positive charge) increases, sodium ion gets “+ve” charge. Similarly, when Chlorine gains one electron, its 102 Teacher Resource Pack Guide Science 7 number of electrons increases than that of protons. Chlorine is now an ion. By gaining one electrons negative charge increases. Therefore, chlorine gets ‘–ve’ sign. 4. How are isotopes important? Describe their uses. Ans: Uses of isotopes: Isotopes can be useful in different industries, such as food, agriculture, archaeology and medicine. Some of their uses are given below: Medicine: In the field of medicine, isotopes (radioactive) are used for radiation therapy. It locates tumors in brain. Some other uses are given in the following chart: Isotope Application in medicine Cobalt-60 Used in radiation therapy to prevent cancer Iodine-131 Locate brain tumors, cure goiter Sodium-24 Study blood circulation Thallium-201 Identify damage in heart tissues Agriculture: In agriculture, isotopes help in various fields as follow: An isotope of Phosphorus (P-32) is used in Phosphorus containing fertilizers. It helps to detect the metabolism of phosphorus in plants. An isotope of carbon (C-14) is used to study the passage of carbon in plants during photosynthesis. 5. How is a chemical formula written? State its rules. Ans: Chemical formula of molecules: The constituents of a molecule and their number can be shown through a chemical formula. A chemical formula is the simplest but comprehensive notation that tells which elements and how many atoms of each element make up a molecule. In a chemical formula, elements making up a molecule are denoted by their symbols. Whereas, number of atoms of each element is written as subscript beside each atom. For example, Methane has one carbon (C) atom and four hydrogen (H) atoms; the chemical formula is CH4. The sugar molecule; glucose has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms, so, its chemical formula is C6H12O6. In the same way, nitrogen that contains two atoms of nitrogen is written as N2, oxygen as O2, fluorine as F2 and iodine as I2. Chemical formula for ionic compounds: When a cation (metal element) chemically combines with an anion (non-metal), a compound is formed. It is an ionic compound. To write the formula of an ionic compound, following steps are used: Step–1: Identify the cation and anion. Write the symbol of cation first and the anion second. 103 Teacher Resource Pack Guide Science 7 Example 1: In compound magnesium chloride (MgCl2), magnesium is a cation and chloride is an anion as: Mg Cl Example 2: In compound aluminum chloride (AlCl3), aluminum is cation and chloride is an anion as: Al Cl Example 3: In compound iron oxide (Fe2O3), Iron is a cation and oxide is an anion as: Fe O. Step–2: Identify the valency of anion and cation. Put the valency number of each ion with its charge on its top right side. Example 1: Mg2+ Cl1Example 2: Al3+ Cl1Example 3: Fe3+ O2Step–3: Crisscross method for writing formula is used to complete the formula. In this method, interchange the valency number of both ions and write them on lower right side of each ion. Omit the +ve and –ve signs. Reduce the ratio by a common factor if possible. 6. Explain the law of constant composition. Ans: The law of constant composition states that composition of a compound is always the same. It means that a compound always contains the same constituents in the same proportion by weight. The factors such as formation method, amount of compound and state of compound do not affect the composition. So, whenever we talk about water, whether it is in liquid state, frozen or in gaseous state, it always has two atoms of hydrogen and one atom of oxygen (H2O). If number of oxygen atoms increases by two, it is not the water now. It has become another compound that is named as hydrogen peroxide (H2O2). It possesses different properties than that of water. Similarly, carbon dioxide (CO2) is a life gas for plants. It possesses two oxygen atoms and one carbon atom. If number of oxygen atoms reduces to one, it turns into another compound named as carbon monoxide (CO). It is highly poisonous and can cause death if inhale even in very minute amount. 7. Make the formula of the following compounds. Ans: 1) Strontium Iodide = SrI2 2) Aluminium Iodide = AlI3 3) Strontium Sulfide = SrS Thick and Solve a. An atom contains five protons. We assume the atom as neutral. How many electrons it must have? Ans: No. of protons = No. of electrons So, atom contains five electrons. Brain Storming! a. The element Zinc (Zn) has atomic number 30. How many protons does it has? Ans: Atomic number is also the proton number. So, it has 30 protons. b. What will be the number of protons in an element has 30 neutrons and its mass number is 55? Ans: Mass number of x = 55 No. of neutrons = 30 No. of protons + No. of neutrons = Mass number No. of protons = Mass number – No. of neutrons = 55 – 30 No. of protons = 25 Activity! 104 Teacher Resource Pack Guide a. Science 7 You have learnt about chemical formulae. Here are given the chemical formulae of some compounds. Study them carefully. i. Write the name of each compound. ii. Guess the valency of each element in each compound. iii. Mention the ions formed (anions as well as cations) in each compound. iv. Make the ionic structure of each ion showing the electronic distribution in different cells and different orbits. a. KF b. K3N c. AlP d. NaH e. LiH f. Ca3P2 g. Ba3P2 h. Al2S3 Ans: 105 Teacher Resource Pack Guide 106 Science 7 Teacher Resource Pack Guide 107 Science 7 Teacher Resource Pack Guide 108 Science 7 Teacher Resource Pack Guide Science 7 Unit # 7 PHYSICAL & CHEMICAL CHANGES & PROCESS Lesson 1 Topic: (7.1: Physical and chemical changes) (7.1.1: Physical changes) Teaching objectives: ⦁ Introduce physical & chemical changes. ⦁ Explain physical changes with examples around us. Key vocabulary: Physical changes chemical changes, melting, freezing, boiling, reversible Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Ice cubes, Burner, Beaker, Display pictures which show changes, Picture of water cycle, salt water. Introduction: Introduce the topic by showing their pictures. Rusting of iron, milk sours or the formation of yogurt, sketching of rubber band, boiling of eggs, removal of stains by freezing of water, detergents, baking of cake, ripening of fruits etc. Ask from students what happened with these things? Tell them they changed from one form to another form. There are two types of changes. “Some changes can be returned and original substance can be obtained. These types of changes are known as Physical changes”. While “many other changes are permanent and cannot be returned to get original substance. These are termed as chemical changes”. Students! Remember both type of changes have their own importance. Today we will discuss physical changes in detail. Let’s start with an activity! Take a can in class and crush it. The shape of the can change but you can easily revive the shape. Crushing of can did not change its composition. The molecules in the can are still the same molecules. These type of changes are known as physical change. These type of changes do not alter the composition of matter. Consider another example by performing an activity. Activity: Take a beaker and put some ice cubes in it. Keep the beaker at room temperature. Soon the ice starts melting and change into liquid water. Keep the water on flame. You notice that after some 109 Teacher Resource Pack Guide Science 7 time the bubbles and steam start appearing in the beaker. It is due to the boiling of water and steam is the vapour of water. If you keep melted water back into freezer it again converts into ice. When you melt an ice cube (H2O) you perform a physical change because you change the state of water and not the chemical composition of water molecule. The water molecules are still the same with two hydrogen and one oxygen atom. Similarly, when water gets boil, it changes its state from liquid to gas. Heating does not alter the chemical combination of water. It remains H2O even in vapour state. Water cycle is the biggest example of physical change in our environment (students already know about it from chapter 5: water). Activity: Take a beaker and add water in it. Put some salt in water and shake it. The salt gets dissolve. It is a physical change. Heat the water unit in the condenser. You will got salt and water again when the water evaporates. How to identify a physical change? Ask students how will you identify a physical change? Tell them: Physical changes alter a substance without changing its chemical composition. This alteration may change some characteristics such as size, shape, state, density, luster, solubility, etc. These characteristics are known as physical characteristics. For example, melting of ice is a physical change which convert solid ice into liquid water. Causes of physical changes: There is always a reason for any change. Physical changes are also caused by different factors such as temperature, light, pressure, etc. For example, the conversion of water into ice is done by temperature change. Physical changes are reversible: Most of the physical changes are reversible i.e., they can 110 Teacher Resource Pack Guide Science 7 easily be returned because structure of molecule does not change. So, no new product formed. Consider the example of water cycle, in which liquid water is converted into vapours by sunlight and than it condense back into rain water. In the whole process the molecule of water (H2O) remains the same. Point to ponder: Keep in mind that all physical changes are not reversible like chopping of wood and breaking of glass are also the physical changes but they cannot be reverse back these are categorized as physical changes because chopping and breaking do not effect its composition. Homework: 1. Define physical changes and give some examples. 2. Learn the definitions of melting, boiling, freezing and sublimation. Conclusion: Ask students about the lecture and answers their questions if any. Tell them we will study chemical changes in the next class. Lesson 2 Topic: (7.1.2: Chemical changes) Teaching objectives: ⦁ Explain chemical changes with examples around us. Key vocabulary: Chemical changes, burning of wood, rusting, browning, of apple, irreversible. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Pictures of chemical changes, Paper, match, stick, rusted iron piece, apple, vinegar, baking soda, beaker, Hydrogen peroxide, cylindrical jar, cups, safety goggle, oil. Chemical changes: First ask students about physical changes. 1. Are physical changes reversible? 2. What type of alterations take place in physical changes? 3. What are the causes of physical change? Start with showing pictures of changes from Lesson 1. Also describe that chemical changes are permanent and cannot return back to its original conditions. Activity: Take a paper and match stick. Burn the paper carefully. The white paper turns into black ash. It is a chemical reaction and paper does not come back into its previous form. The composition of paper changes due to burning. Burning: Burning is a chemical change. When wood, paper or coal burns, materials in the wood combine with oxygen in the air. They form ash, smoke and carbon dioxide. These substances are different from wood and cannot be converted back to wood. Rusting of iron: Rusting of iron is also a chemical change. Iron forms rust when it reacts with oxygen in the presence of water. Rust is not iron or oxygen. It is a new material. Show the piece of rust to students. Activity: Take a piece of apple. Cut into 4 pieces, show the students and keep it in a plate for an hour or two. Ask the students what happens with the apple? They answer that the apple changes its color from white to brown. Tell them the change in color is due to chemical reaction. Browning of apples: Cutting of apple damages its cells, it allows the oxygen in the air to react with the constituents in the apple. The reaction cause browning of apples. Tarnishing of metal: Silver spoons get tarnished after some time. This tarnish is different from silver. The black tarnish occurs due to oxidation of silver. Show the picture of tarnished spoon. Students you have noticed in the above examples that original substances changed into new substances that cannot be obtained book. These changes are called chemical changes. Material: 3 empty cups, an apple cut into 3 slices. Chemicals: Water, oil, vinegar. What to do: Take tittle amount of water, oil and vinegar in different cups. Put one slice of apple in a cup of water, other in vinegar and third one in oil. Stay them unshaven for one hour. Observe what happens to the apple slices and answer the questions. 1. What would happen to each slice of apple in different substances? 111 Teacher Resource Pack Guide Science 7 2. Which of the three chemicals speed up or slow down the chemical change? How to identify a chemical change? Following are some signs of chemical change. If two or more signs occur during a change, you must be observing a chemical change. 1. Production of an odour: Some chemical changes result in the production of smell. When an egg decays, smell of sulfur produces, which indicate a chemical change. 2. Change in temperature: Often chemical changes result in the change in temperature. You must have observed that the temperature is higher when the logs are burning. 3. Change in colour: A change in colour is also an example of chemical change. For example, the colour of bread changes when it is rotten. 4. Formation of bubbles: When we mix antacid tablet with water, it begins to bubble. When the gas bubbles form, it indicates the chemical change. 5. Formation of a solid: When we combine two liquids, solid called precipitate can form. It is also an indication of chemical change. Activity: Perform the following activity to identify a chemical change. Three containers with lids Three food colour (different) Three droppers Bleach Vinegar Hydrogen peroxide Procedure: 1. Half fill three containers with water. 2. Add 2-3 drops of three food colours in three containers (one colour in one container). 3. Label the containers as A,B,C. 4. In container, add one dropper full of vinegar. 5. In container B, add a dropper full of bleach. 6. In container C, add a dropper full of hydrogen peroxide. 7. Put the lid on all the three containers and stir them well. 8. Identify in which container the chemical change has occurred. The chemical change has occurred in the container B and C. 9. How do you identify that it is a chemical change. The food colour discharge in the pressure of hydrogen peroxide and bleach, which shows a chemical change. Causes of chemical change: Chemical change is one that affects the chemical composition of the substance. New compounds are formed as a result of chemical change. These new compounds exhibit properties that are different from parent (reacting) substances. The difference in properties is because atoms rearrange themselves. Activity: Ask students about the example of chemical change in daily routine which uses kitchen chemicals as reacting substances. Here is an example of chemical change from kitchen. Your mother pours vinegar to baking soda to clean kitchen shelves. When vinegar (acetic acid) comes in contact with baking soda (sodium bicarbonate), bubbles arise and sodium acetate forms. These bubbles are due to the release of carbon dioxide gas. Chemical changes are irreversible: Chemical changes are irreversible. They cannot give the reacting substances back. In the above example vinegar and soda form sodium acetate and gives out carbon dioxide. It cannot give vinegar and soda back, even if your reverse all the conditions. Homework: How can we term a change as chemical change? Conclusion: Discuss main points of the topic again. Tell them we will compare physical and chemical changes in the next lecture. Lesson 3 Topic: Teaching objectives: 112 (Comparison of physical and chemical change) ⦁ Explain physical and chemical changes occur side by side. Teacher Resource Pack Guide Science 7 ⦁ Discuss comparison of physical and chemical changes. Key vocabulary: Physical change, chemical change. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Candle, Match stick. Physical and chemical changes may occur simultaneously! Sometimes, physical and chemical both change take place in a single phenomenon such as burning of candle. When a candle burns, its wax melts and changes to vapour state. There are the physical changes of state as the war whether solid, liquid, or vapours are still the same substance. During the burning, some of the wax vaporizes and produces water vapours, carbon dioxide gas, heat and light. These changes involve the chemical composition of wax and cannot be returned. Hence, these are chemical changes. Activity! Perform the activity and solve the worksheet. Burn a candle. Ask students to mention physical and chemical change in the candle and fill the worksheet. Physical changes: _____________________ ____________________________________ Chemical changes: ____________________ ____________________________________ Comparison between physical and chemical changes: Ask students to point out the differences between physical and chemical change and write these points in board. No. Physical changes No. Chemical changes 1. Physical changes alter a substance without 1. Chemical changes affects the chemical changing its chemical composition. composition of the substances. 2. Physical changes do not produce new 2. Chemical changes produce new compounds. compounds which are totally different from parent substances. 3. Physical changes are mostly reversible. 3. Chemical changes are mostly irreversible. 4. Structure of molecules does not change in 4. Structure of molecules change in chemical physical change. change. 5. Physical change can be identified by 5. Chemical changes can be identified by change in size, shape, density, state, loser, change in odour, temperature, colour, solubility, etc. formation of bubble and formation of solid. Activity: Solve the worksheet. Identify physical and chemical changes from the following examples. also mention the reason of identification. Example Physical / Chemical Reason A man eating chocolate bar Boiling of egg in water 113 Teacher Resource Pack Guide Science 7 Burning of candle Activity Perform the activity 7.2 from CSS – Science – 7 Homework: Make a comparison between physical changes and chemical changes. Conclusion: Revise the students all the main points. Tell them we will study importance of chemical changes in our next lecture. Lesson 4 Topic: (7.2: Why are chemical changes important?) (7.2.1: Use of hydrocarbons as full) (7.2.2: Vegetable fat is a gift of chemical change) Teaching objectives: ⦁ Discuss importance of chemical changes with examples: (a) Hydrocarbons as fuel (b) conversion of oil into ghee Key vocabulary: Fossil fuels, hydrocarbons, exothermic, hydrogenation, Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Oil, ghee. Introduction: Tell the students that we are living in the world of chemical changes. Nearly everything with which we have daily contact is the product of a chemical change. Burning of fossil fuels, synthesis of plastic, synthetic fertilizers, digestion of food etc. all are the gifts of chemical changes. We will discuss some of the benefits in detail in today’s class. Explanation: A fuel is a substance which is used as a source of energy. This energy is mostly in the form of heat. Fossil fuels are obtained from natural resources. Fossil fuels primarily are hydrocarbons i.e. compounds made of carbon and hydrogen. These hydrocarbons when heated, react with air (oxygen) and undergoes combustion reaction. This reaction is exothermic that gives new compounds (CO2, H2O) and generates more energy in the form of heat. Fossil fuel + oxygen Carbon dioxide + water + energy (Methane) CH4 + 2O2 CO2 + 2H2O + energy This heat, when produced in large amounts, is utilized to accomplish many purposes i.e. power generation, warming homes, powering cars, etc. Hydrogen fuels are generally called fossil fuels. These are naturally found in all the three states of matter i.e. solid (coal), liquid (petroleum) and gas (natural gas: methane; CH4). Effect of hydrocarbons on environment: Besides carbon and hydrogen, these hydrocarbons contain Sulphur and nitrogen in small quantities. When fuel is burnt, these elements also react with air (oxygen) producing (SO2, NO2, NO, CO2, etc). Carbon dioxide is a potential cause of global warming. When these oxides dissolve in water, they produce respective acids (H2SO4, HNO3, H2CO3). These acids cause acid rain that increases the soil acidity and pollute the environment. The burning of fossil fuels produces greenhouse gases. These gases trap the sun rays inside the Earth and causing increase in global temperature. Activity: Tell the students about renewable and non-renewable energy resources. Separate out renewable and non-renewable from the following list. Oil Methane Coal Sun Hydropower Wind Wood Vegetable fat is a gift of chemical change: Vegetable fat is used in eastern cuisine. It is the transformation of vegetable oil through a process called hydrogenation. In this process, hydrogen gas is passed through vegetable oil that converts it into fats. During hydrogenation, temperature is maintained at 60°C. “A catalyst is a substance that enhances the chemical reaction without being used in it”. A nickel catalyst speeds up the reaction. Oils (mustard oil, linseed oil, olive oil, corn oil, etc.) are converted into solid or semisolid fat (ghee) which have higher melting points as well. The equation for the process of hydrogenation is as follow: 114 Teacher Resource Pack Guide Science 7 60°C Hyrogen + vegetable oil vegetable fat (ghee). Ni As reaction starts, large amount of heat is produced. So, hydrogenation is an exothermic process. Activity: Take a sample of ghee and oil in the jar. Show the students and tell them to observe the difference between them. Heat the ghee on flame and ask about the type of change. Solve the question after performing activity. 1. Tell the difference between oil and ghee. 2. Formation of ghee from oil is a chemical change or physical change? 3. What happen when we heat the ghee on flame? 4. Is heating the ghee is a physical change or a chemical change? Homework: 1. Give an equation for combustion reaction. 2. Give an equation for conversion of vegetable oil into fat. Conclusions: Revise all the main points from board. Conduct reading by students with correct pronunciation. Answer the students questions if any. Inform them about the next day lesson i.e., use of fertilizers in agriculture. Lesson 5 Topic: (7.2.2: Use of fertilizers in agriculture) Teaching objectives: ⦁ Discuss the importance of chemical changes with examples of fertilizers. Key vocabulary: Synthetic fertilizers, hardness, hygroscopicity. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Sample of fertilizer. Introduction: Planks take nutrients from soil. Sometimes, due to excess farming at the same place, soil gets worn out and could not provide sufficient nutrients to plants. Therefore farmers have to add fertilizers. “A fertilizer is any substance added to the soil to make it more fertile”. It may be natural or synthetic. Explanation: Animal manure is a natural fertilizer. Synthetic fertilizers are made in factories by chemical reactions. These fertilizers provide nutrients like nitrogen, phosphorous and potassium which are essential for plant growth. Here are some examples. Ammonium nitrate [NH4NO3] Ammonium sulfate [(NH4)2 SO4] Potassium sulfate [k2 SO4] Ammonium phosphate [(NH4)3 PO4] Properties of synthetic fertilizers: 1. Synthetic fertilizers are made through chemical reactions between different compounds. 2. Chemical properties of fertilizers are about the nutrients they provide such as nitrogen, phosphorus and potassium. 3. Physical properties of fertilizer such as particle size, hardness, hygroscopicity etc. tell us the efficacy and convenience of fertilizer in use. 4. Fertilizers with small particle size dissolve easily in water but it should not be less than 5 millimeters. Otherwise, it would create dust and loss of fertilizer. 5. Hard particles are better than soft particles of fertilizers, because they release nutrients gradually. 6. Hygroscopicity is the property of absorbing moisture from the air. It also effects the fertilizers stability. Activity: Show the sample of fertilizer to the students. So that they can understand its physical properties easily. Harmful effects of fertilizers: Fertilizers help to feed the world. We could not grow enough crops without them. But there are drawbacks as well! 1. Threat for aquatic life: Fertilizers run off can seep into rivers and other water bodies. 115 Teacher Resource Pack Guide Science 7 Here, phosphorus from fertilizers, facilitate the growth of algae. Algae grows over large surface area and blocks the sunlight to penetrate deep into water. After its decay, bacteria decompose them by using the dissolved oxygen of water. Thus the oxygen level get reduced. Hence, aquatic life suffer. 2. In the water supply: River water or ground water is supplied to our houses. This may contain seeped fertilizers. The nitrogen from fertilizers combine with hemoglobin instead of oxygen thus, reducing its level in the body. Insufficient supply of oxygen may cause sickness due to which skin may take bluish tinge. Homework: 1. Give at least two examples of natural fertilizers? 2. Give at least two examples of synthetic fertilizers? 3. How are fertilizers pose a threat for environment? Discussion: Revise all the main points from board. Conduct reading with correct pronunciation. Answer the students’ questions if any. Inform them about the next day lesson i.e. plastics. Lesson 6 Topic: (Plastics) Teaching objectives: ⦁ Discuss the importance of chemical changes in the preparation of plastics. Key vocabulary: Polymerization, ethylene, styrene, propylene. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Plastic bag, plastic toys, plastic items. Liquid glass, borax solution, food colouring, water, bowls. Introduction and development: You know that, molecules are group of atoms. Similarly, plastics are group of molecules liked together in the form of chains. These chains are called polymers and the formation of polymers is called polymerization. The word ‘poly’ mean many and ‘mer’ means units. So, plastics are the substances made by linking up many units. For example: Polyethylene made by ethylene units. Polystyrene made by styrene molecules. Polypropylene made by propylene molecules. The single unit of polymer (plastic) is called monomer. The polymer (plastics) molecules mainly contain carbon and hydrogen and in minute amount sulfur, chlorine, fluorine, phosphorus or silicon may also be present. Activity: Show the different items made from plastics and as following questions: Toys, plastic bags, plastic utensils, tooth brush, plastic bottles. 1. Are they flexible or bend easily? 2. Are they colourful? 3. Does water affect them? 4. Does sunlight melt them? 5. Does they get corrode? Plastics production: Plastics are also the gift of chemical reactions. Most plastics are made from naphtha. Naphtha is obtained from petroleum through fractional distillation. Naphtha is subjected to a cracking process. In this process, complex organic chemical compounds of naphtha are broken down into smaller molecules. These smaller molecules are hydrocarbons. Ethylene (C2H4) is mostly obtained as a result of cracking of naphtha. “Cracking is the breakdown of larger compounds into smaller molecules”. Hundreds and thousands of ethylene molecules are linked up together forming polymer named polyethylene. It is in the form of pellets. These pellets are then melted and molded into desired shapes. Activity Perform the activity 7.4 from CSS – Science – 7 Homework: 1. What are plastics? How are they manufactured? Conclusion: Revise all the main points from board. Conduct reading with correct pronunciation. Answer the students’ questions if any. Inform them about the next lesson, “reversible and irreversible reaction”. 116 Teacher Resource Pack Guide Science 7 Lesson 7 Topic: (7.3: Reversible and Irreversible reactions) Teaching objectives: ⦁ Discuss reversible and irreversible reactions. Key vocabulary: Single head arrow, two sided arrow. Materials required: ⦁ Board (black/white), Marker / Chalk, CSS – Science – 7, Chocolate, flour dough, ghee, orange juice, sugar, newspaper, milk. Introduction and development: Tell the student from previous lectures that physical changes are reversible which chemical changes are irreversible. Following are the main difference between reversible and irreversible reactions. No. Physical changes No. Chemical changes 1. The reactions which are easy to reverse 1. These reactions which are unable to are called reversible reactions. reverse are called irreversible. 2. Reversible reactions be proceed in either 2. Irreversible reactions can proceed in directions. single directions. 3. Reversible reactions are denoted by two 3. Irreversible reactions are denoted by single head arrow (). sided arrow ( ). 4. Physical changes are mostly reversible. For example: A block of ice melts to form water. 4. Chemical changes are mostly irreversible. For example: Hydrocarbons burn to procedure carbon dioxide and water. Water boils to form steam. Iron rusts to form iron oxide. Activity: Identify reversible and irreversible reactions and give the reason. Also write equations. 1. When blue copper sulphate crystals are heated, they lose their water of crystallization. Blue colored crystals turn into white copper sulphate. After cooking, if water is added to this white powder, the blue color immediately returns. (Give pictures as well). Copper sulphate (Blue) 2. Heat Water Copper sulphate (White) Burn the wood. It is converted into ash and smoke. It also gives heat. (Give pictures). Burn Wood Heat + Ash + Smoke Activity: Heat the following materials and complete the given table. Material Appearance Appearance Observation before heating when heated after heating Chocolate Flour dough Ghee Orange juice Sugar Newspaper Milk Reversible / Irreversible? Review Exercise A. 1. Choose the correct answer and fill the circle. The change in matter that can be reversed is called: chemical change physical change permanent change physical but permanent 117 Teacher Resource Pack Guide Science 7 “Bread becoming toast” is a chemical change. Which of the following features proves it as chemical change? the colour of bread changes toast cannot be returned into slice the size of bread changes heating did not change its composition 3. Identify the process responsible for chemical change: sublimation condensation photosynthesis freezing 4. “Paper towel absorbs water”. What kind of change it represents? chemical change permanent change irreversible change physical change 5. Marble statue damages when acid rain falls on it. It is a chemical change because: composition of marble change marble can be returned to original state state of marble change CO2 gas produced 6. Which of the following processes is responsible to generate heat in hydrocarbons? cracking combustibility fractional distillation condensation 7. CH4 + 2O2 CO2 + 2H2O In the above equation, which compound undergoes combustion reaction? CH4 O2 CO2 H2 O 8. Hydrogenation is a chemical reaction. Its product is: plastics fertilizers vegetable fat heat energy 9. The raw material in production of plastic is: naphtha vegetable oil methane gas ammonia 10. Identify the reaction responsible for plastic making: hydrogenation polymerization combustion fractional distillation 11. Reactions in which products cannot be turned back into reactants are termed as: irreversible reactions reversible reactions equilibrium reactions redox reactions 12. Which of these is a reversible change? metal rusting baking a cake freezing orange juice to make ice lolly wood burning 13. Which of these statements is FALSE? boiling is not a reversible change dissolving is a reversible change heating a substance can cause both reversible and irreversible change most of chemical changes are reversible 14. If you are burning a candle, which of the following would be a reversible change while a candle is burning? the solid wax melts the liquid wax in the wick burns the flame produces smoke all of the above 15. Which of the following symbol is the representation of reversible reactions? none of these B. Read each condition. Decide, is it a physical change or chemical change. Give reason for your decision. The first one has been done for you. No. Condition Physical or Evidence… Chemical Change? 1. A student removes a loaf of bread hot a. heating of slice is a a. change in colour from the oven. The student cuts a slice chemical change cannot be returned. of the loaf and spreads butter on it. b. cutting of slice and b. No change in 2. 118 Teacher Resource Pack Guide 2. Ali has forgotten to take out an egg from oven. He wanted to make it cook. But it has now burst and its pieces have sticken to the walls of oven due to long exposure to microwaves. But the good thing is, it is cooked. 3. You cut the lemon with fruit knife but forgot to wash it afterward. Now, blackish brown spots have been appeared on it. Science 7 spread of butter is physical change a. cooking of egg is a chemical change b. bursting is a physical change composition, no new compound is formed. a. In cooking the composition of egg change. b. In bursting no change in composition occur. a. Cutting is a physical change. b. Appearance of spots is a chemical change. a. In cutting no change in composition takes place. b. Change in color shows chemical change. a. Only the shape of hair changes. a. Cake cannot go back into its previous spots. 4. You stylized your hair with thermal a. Physical change roller. 5. While making cake, you added baking a. Chemical change powder. It made the cake rise by releasing carbon dioxide gas. 6. Your hair colour changes when you a. Physical change a. The condition is colour them. But the original colour reversible. regains after sometimes. B. Answer the following questions briefly. 1. Define physical changes and give some examples. Ans: “Physical changes alter a substance without changing its chemical composition”. For example: freezing of water, boiling of water, filling of air in balloon etc. 2. How can we term a change as chemical change? Ans: Chemical change is one that affects the chemical composition of the substance. New compound are formed as a result of chemical change. 3. Give an equation for combustion reaction. Ans: CH4 + 2O2 CO2 + 2H2O + energy 4. Give at least two examples of synthetic fertilizers. Ans: Ammonium nitrate [NH4NO3] Ammonium sulfate [(NH4)2 SO4] 5. Why are plastics called polymers? Ans: Polymers are given the name-plastics because of their ability to be mold easily. The word plastic has Greek origin which means to be able to be shaped a moulded by heat easily. 6. How are reversible changes related to physical changes? Ans: Physical charges are also reversible so, both are related to each other. Like melting of ice is a reversible as well as a physical change. 7. Could any chemical change be reversible? If yes, give example. Ans: There are some chemical changes that can be reversed. Such changes take place in closed system e.g., formation of ammonia. 8. Size and texture are physical properties of fertilizers. How do they affect the utility of fertilizer? Ans: Fertilizers with small particle size dissolve easily in water but it should not be less than 5 millimeters. It would create dust and loss of fertilizer. Similarly hard particles are better than soft ones because they release nutrients gradually. 119 Teacher Resource Pack Guide C. 1. Ans: 2. Ans: 1. 2. 3. 4. 5. 3. Ans: Science 7 Answer these questions in detail. Make a comparison between physical changes and chemical changes. Given in Lesson No. 3. How would you identify a chemical change? How to identify a chemical change: Following are some signs of chemical change. If two or more signs occur during a change, you must be observing a chemical change. Production of an odour: Some chemical changes result in the production of smell. When an egg decays, smell of sulfur produces, which indicate a chemical change. Change in temperature: Often chemical changes result in the change in temperature . You must have observed that the temperature is higher when the logs are burning. Change in colour: A change in colour is also an example of chemical change. For example, the colour of fruit changes when it is rotten. Formation of Bubbles: When we mix antacid tablet with water, it begins to bubble. When the gas bubbles form, it indicates the chemical change. Formation of a solid: When we combine two liquids, solid called precipitate can form. It is also an indication of chemical change. How could you convert vegetable oil into fat? Vegetable fat is used in eastern cuisine. It is the transformation of vegetable oil through a process called hydrogenation. In this process, hydrogen gas is passed through vegetable oil that converts it into fats. During hydrogenation, temperature is maintained at 60ºC. A nickel catalyst speeds up the reaction. Oils (mustard oil, linseed oil, olive oil, corn oil, etc.) are converted into solid or semi-solid fat (ghee) which have higher melting points as well. The equation for the process of hydrogenation is as follow: 60°C Hyrogen + vegetable oil vegetable fat (ghee). Ni As reaction starts, large amount of heat is produced. So, hydrogenation is an exothermic process. 4. Synthetic fertilizers provide nutrients to plant. On the other hand, they cause pollution. How? Ans: Synthetic fertilizers are made through chemical reactions between different compounds. Chemical properties of fertilizers are about the nutrients they provide such as nitrogen, phosphorus and potassium. Whereas, physical properties such as particle size, hardness, hygroscopicity etc. tell us the efficacy and convenience of fertilizer in use. Fertilizers with small particle size dissolve easily in water but it should not be less than 5 millimeters. It would create dust and loss of fertilizer. Similarly, hard particles are better than soft ones because they release nutrients gradually. Hygroscopicity is another property that affects the fertilizer’s stability. Harmful effects of fertilizers: Fertilizers help to feed the world. We could not grow enough crops without them. But, there are drawbacks as well! 1. Threat for aquatic life: Fertilizers run off can seep into rivers and other water bodies. Here, Phosphorus from fertilizers, facilitate the growth of algae. Algae grow over large surface area and check the sunlight to penetrate deep into water. After its decay, bacteria decompose them by using the dissolved oxygen of water. Thus, the oxygen level gets reduced. Hence, aquatic life suffers. 2. In the water supply: River water or ground water is supplied to our houses. This may contain seeped fertilizers. The nitrogen from fertilizers combine with hemoglobin instead of oxygen thus, reducing its level in the body. Insufficient supply of oxygen may cause sickness due to which skin may take bluish tinge. 120 Teacher Resource Pack Guide Science 7 5. What are plastics? How are they manufactured? Ans: Plastics: In your previous class, you have studied that molecules are group of atoms. Similarly, plastics are group of molecules linked together in the form of chains. These chains are called polymers and the process of the formation of polymers is called polymerization. The word ‘poly’ mean many and ‘mer’ means units. So, plastics are the substances made by linking up many units such as polyethylene (made by ethylene units), polystyrene (made by many styrene molecules) and polypropylene (made by many propylene molecules). The single unit of polymers (plastics) is called monomer. The polymer (plastics) molecules mainly contain carbon and hydrogen and in minute amount sulphur, chlorine, fluorine, phosphorus or silicon may also be present. Plastics production: Plastics are also the gift of chemical reactions. Most plastics are made from naphtha. Naphtha is obtained from petroleum through fractional distillation. Naphtha is subjected to a cracking process. In this process, complex organic chemical compounds of naphtha are broken down into smaller molecules. These smaller molecules are hydrocarbons. Ethylene (C2H4) is mostly obtained as a result of cracking of naphtha. Hundreds and thousands of ethylene molecules are linked up together forming polymer named polyethylene. It is in the form of pellets. These pallets are then melted and moulded into desired shapes. Activity – 1: You have studied following techniques and processes. Identify them as physical or chemical change. (i) Solubility is a physical change because no change in chemical composition occurs. (ii) Filtration is a physical change because it is a reversible process. (iii) Distillation is a physical change because it is reversible. (iv) Combustion is a chemical change because it is irreversible and chemical composition changes after combustion. (v) Evaporation is a physical change because chemical composition does not change in evaporation. Activity – 2: During load shedding at night, Wahaj lit four identical candles. He placed three candles very close (side by side) at his study table for more light, And one on dining table. When the power came back an one hour later, wahaj was surprised to see that the candles in the group were much shorter than the one at dining table. There was more wax around the candles in group. What would cause the candles inn group to burn early? Which process yielded the wax around on the table? 1. What would cause the candles in group to burn early? Ans: Candles in group receive more heat because they are close to each other. That’s why they burn early than single candle on dining table. 2. Which process yielded the wax around on the table? Ans: Melting of was. Activity – 1: Material: 3 empty cups, An apple (cut it into three slices) Chemicals: water, oil, vinegar What to do: Take little amount of water, oil and vinegar in different cups. Put one slice of apple in a cup of oil, other in vinegar and third one in water. Stay them unshaken for one hour. Observe what happens to the apple slices. Questions to think: 1. What would happen to each slice of apple in different substances? Ans: The slice in oil does not change color, the slice in vinegar slightly change its color, while the slice in water turns brown. 2. Which of the three chemicals speed up or slow down the chemical change? 121 Teacher Resource Pack Guide Science 7 Ans: Oil slows down the change because it forms layer on apple and stops oxygen interaction. Water speeds up the reaction by providing more oxygen. While vinegar has little effect. Activity Heat the following material and complete the table. Material Appearance Appearance Observation Reversible / before heating when heated after heating Irreversible? Chocolate Solid Liquid Solid Reversible Flour dough Wet solid Dry solid Dry solid Irreversible Ghee Semi-solid Liquid Semi-solid Reversible Orange juice Liquid Boiling liquid Liquid Reversible Sugar Solid Liquid Liquid Irreversible Newspaper Solid Ash Ash Irreversible Milk Liquid Boiling liquid Liquid Reversible Unit # 8 TRANSMISSION OF HEAT Lesson 1 Topic: (8.1: The cause of flow of heat) Teaching objectives: ⦁ Recall energy and work. ⦁ Recall kinetic energy and give examples. ⦁ Recall potential energy and give examples. ⦁ Recall heat as kinetic energy. ⦁ Introduce hot body and cold body. ⦁ Explain the flow of heat. Key vocabulary: Energy, work, stored, working, kinetic, potential, hot body, cold body, heat, transit. Materials required: ⦁ Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. A glass of hot water, and a glass of icy water for classroom activity. Background: The purpose of this unit is to revise heat and introduce the transmission of heat. It will help the students to understand how flow of heat takes place. At this level, students have no prior knowledge of transmission of heat. Now, they will be introduced to this process for the first time. Introduction: Ask the students: How does water boil? What happens before and after the process? Write the responses on writing board. Tell the students that today we will be learning what energy transit means and how it flows from hot body to cold body. (The teacher will announce that today we are going to begin 8th chapter from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that from our previous knowledge, we know that energy is necessary for bodies to do work. We have also studied in earlier classes that energy has many forms. One of those forms is heat. Its nature is kinetic, and is a form of energy that is in transit (transfers from one body to another). In this chapter, we shall deal with the questions, such as: 1) What causes flow of heat between two bodies? 2) How does flow of heat take place or what are the modes of flow of heat? 3) What are the applications of transfer of heat? We sense hotness and coldness in daily life. Some objects are hot such as a hot cup of tea. Others are cold such as a cold drink of coke. An important point to remember here is that a hot body does not have more heat. It has more thermal energy and it is hot because it is at high temperature (degree of hotness). On the other hand, a cold body possesses low temperature. 122 Teacher Resource Pack Guide Science 7 When hot and cold bodies are brought closer to each other, the hot body transfers some of its thermal energy to the cold one. In this way, the thermal energy and temperature of the hot body decrease and it cools down. The thermal energy and temperature of the cold body increase and it heats up. This transfer of thermal energy is called the flow of heat. So, heat is thermal energy in transit. The flow of heat continues till the thermal energies of both the bodies become the same. Classroom Activity (Page 102 on book): Add hot water in one glass. Put ice in water of other glass. Shake the ice-water to make it cold. Dip your finger for just a moment in hot water and feel its hotness. Repeat this process with cold water glass. Now mix both hot water and cold water in a jug. Shake the jug to mix them. Now feel the mixed water in the jug. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is work? What is energy? 2. How does energy produce work? What does it mean by stored? 3. What is potential energy? What does it mean by working? 4. What is kinetic energy? Is heat kinetic energy? 5. What does energy in transit mean? What are hot and cold bodies? 6. How does heat flow? Lesson 2 Topic: (8.2: Modes of flow of heat) (8.2.1: Conduction) Teaching objectives: ⦁ Recall the flow of heat. ⦁ Introduce modes of heat flow. ⦁ Clearly define and explain conduction. Key vocabulary: Energy, work, stored, working, kinetic, potential, hot body, cold body, heat, transit, conduction, solids, vibrate, free electrons. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Metal rod, wax, candle, wooden bock with a groove for classroom activity. Background: The purpose of this topic is to introduce modes of heat transfer and explain conduction in solids. It will help the students to understand the difference between conductors and insulators. At this level, students have no prior knowledge of conduction. Now, they will be introduced to this process for the first time. Introduction: Ask the students: Why do we use metal pots for cooking? Does all the metal get hot instantly when the fire is turned on? Write the responses on writing board. Tell the students that today we will be learning how solids such as metals get hot by a mode of heat transfer called conduction. (The teacher will announce that today we are going to topic 8.2 from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that in the previous section, we came to know that heat is transferred from hot to cold bodies due to the difference in their thermal energies. Now the question arises that how does this flow of heat take place? We are familiar with the three states of matter: solid, liquid and gas. The way in which flow of heat takes place depends on the states of matter. There are three modes of flow of heat: Conduction, Convection, and Radiation. In this section we will study these three modes of flow of heat with the help of experiments. The first mode of flow of heat is conduction. It takes place in solids. In solids, the particles are almost fixed in their places under the influence of strong attractive forces. Particles of a solid can only vibrate about their fixed positions. So, during conduction of heat in a solid, the particles that have more thermal energy (particles of hotter region) share it with the nearby particles of low thermal energy 123 Teacher Resource Pack Guide Science 7 (particles of colder region). The particles of the conductor i.e. solid (or medium) only share their thermal energy. They do not move from hot to cold region themselves. Hence, conduction can be defined as, “The process of flow of heat without the flow of the particles of the medium is called conduction.” Among solids, some conduct heat very quickly. They are called good conductors. For example, metals such as iron and steel get hot very quickly. Solid materials such as wood, plastic etc. (non-metals in general) conduct heat very slowly. They are called bad conductors or insulators. Classroom Activity (Page 104 on book): Fix the metal rod in the groove of the wooden block. Apply wax on the one end (B) of the rod. Let the wax cool and solidify. Light up a candle and place it under the other end (A) which is without wax. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like: 1. What is kinetic energy? Is heat kinetic energy? 2. What does energy in transit mean? 3. What are hot and cold bodies? 4. How does heat flow? What are the modes of heat transfer? 5. What is conduction? How and where does conduction occur? Lesson 3 Topic: (8.2.2: Convection) Teaching objectives: ⦁ Recall liquid and gas. ⦁ Recall particles and their movement. ⦁ Clearly define and explain convection. Key vocabulary: Energy, work, stored, working, kinetic, potential, hot body, cold body, heat, transit, liquid, gas, convection, convection current, sink, rise. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Round-bottom flask, Potassium Permanganate crystals, Bunsen burner, tripod stand, mesh for classroom activity. Background: The purpose of this topic is to introduce and explain convection in liquids and gases. It will help the students to understand how transfer of heat takes place in liquids and gases where conduction fails. At this level, students have no prior knowledge of convection. Now, they will be introduced to this process for the first time. Introduction: Ask the students: How does a fan cool a room? Write the responses on writing board. Tell the students that today we will be learning how liquids and gases get hot by a mode of heat transfer called convection. (The teacher will announce that today we are going to topic 8.2.2 from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that the states of matter other than solids are liquids and gases. In liquids, atoms are still close to each other but they can move with more freedom than in solids. Particles of a gas are totally free and have large spaces between one another. They move randomly. As a result, conduction is no longer an efficient mode of flow of heat in liquids and gases. Therefore, heat flows in liquids and gases by convection. During convection not only the thermal energy of the particles but also the particles themselves move or flow from the hotter region to the colder region. This flow of particles during convection is called convection current. Hence, we can define convection as, “Flow of heat by the flow of the particles of the medium from hotter to colder region is called convection.” Classroom Activity (Page 105 on book): Fill the round-bottom flask with water. Pour Potassium permanganate crystals in water, but do not mix them. Let the crystals settle at the 124 Teacher Resource Pack Guide Science 7 bottom. Put the flask on the mesh and place it on the tripod stand. Put the burner under the tripod and turn the flame on. The mode of heat transfer is convection. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like: 6. How does heat flow? What are the modes of heat transfer? 7. What is convection? How and where does convection occur? 8. How is it different from conduction? Lesson 4 Topic: (8.2.3: Radiation) Teaching objectives: ⦁ Recall solid, liquid, gas and vacuum. ⦁ Introduce electromagnetic radiation. ⦁ Clearly define and explain radiation. ⦁ Clearly define and explain emission and absorption. ⦁ Explain the differences between good and bad radiators. Key vocabulary: Medium, vacuum, electromagnetic, radiation, emission, absorption, texture. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Two tin cans (one rough, one shiny) and two thermometers for classroom activity. Background: The purpose of this topic is to introduce and explain radiation in vacuum. It will help the students to understand how transfer of heat takes place in empty space where conduction and convection fail. At this level, students have no prior knowledge of convection. Now, they will be introduced to this process for the first time. Introduction: Ask the students: How does a microwave oven heat food? Write the responses on writing board. Tell the students that today we will be learning how heat is transferred even when there is no solid, liquid or gas. (The teacher will announce that today we are going to topic 8.2.3 from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that the absence of any medium (solid, liquid or gas) is called vacuum. We have studied the ways in which flow of heat takes place in solids, liquids and gases. How does the heat of the Sun reach the Earth whereas there is space between Earth and Sun? In other words, can heat flow through vacuum? If it does, what is the mode of transfer? The answer to the above questions is yes. Heat does flow through vacuum and the mode of transfer is radiation. The name “Radiation” is used for the waves which can carry energy (in the form of light and heat) through vacuum. These waves are called electromagnetic radiation. So, we can define radiation as, “The mode of flow of heat through vacuum with the help of electromagnetic waves is called radiation.” During the process of flow of heat by radiation, a hot body gives out heat in the form of radiation. This process is called emission. These radiations (electromagnetic waves) carry heat energy to the cold body. The cold body receives this heat by a process called absorption. Just as there are conductors and insulators, there are good radiators and bad radiators. Good radiators emit as well as absorb heat better than bad radiators. The amount of heat that is transferred by radiation depends on the properties of the surface of the body. If the surface of the body is made up of a good radiator then it will be able to emit and absorb more heat. Consult the table on page 107 to compare the properties of good and bad radiators. Classroom Activity (Page 107 on book): Fill the cans with water and close the lids. Fix the thermometers in the holes of the lids. Thermometers must be dipped in the water. Place both cans in bright sunlight. Keep recording the temperature on both thermometers at regular intervals. Empty the cans fill them with boiling water and close the lids. Fix the thermometers in the holes of the lids. Keep recording the temperature on both thermometers at regular intervals. 125 Teacher Resource Pack Guide Science 7 Answers: Mode of transfer of heat between cup and environment is radiation. In the first case, the rough black can absorbs more heat. So its temperature rises more. In the second case, rough black can emits more heat. So its temperature falls more. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like: 1. What are the modes of heat transfer? What is vacuum? 2. What are electromagnetic waves? How and where does radiation occur? 3. How is it different from conduction and convection? Lesson 5 Topic: (8.3: Flow of heat in the Environment) Teaching objectives: ⦁ Recall conduction, convection and radiation. ⦁ Introduce thermal expansion. ⦁ Introduce land breeze. ⦁ Introduce sea breeze. ⦁ Explain wind formation. ⦁ Explain gliding of birds. ⦁ Introduce ocean currents. ⦁ Explain thermal vision. Key vocabulary: Thermal, expansion, land, sea, breeze, wind, gliding, glide, glider, ocean, current, thermal, vision. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce and explain that heat transfer occurs in the environment. It will help the students to understand different natural processes for which conduction, convection, and radiation are responsible. At this level, students have no prior knowledge of these processes. Now, they will be introduced to them for the first time. Introduction: Ask the students: Why gaps are left between roads? How do winds blow? Why do beaches remain cool? Write the responses on writing board. Tell the students that today we will be learning how heat transfer causes some natural processes which are important. (The teacher will announce that today we are going to topic 8.3 from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that until now, we have studied that heat flows from hot to cold bodies by three methods: conduction, convection and radiation. We have also designed experiments to demonstrate these modes. Now we will study how these modes of flow of heat occur in nature and affect the environment. Let us begin with conduction. Conduction can be dangerous for buildings and structures made of solids. The following paragraph shows how. Not only do solids conduct heat but also expand due to rise in their thermal energy. To avoid cracking due to expansion, empty spaces are left between slabs of construction materials such as concrete, asphalt etc. The same precaution is taken during building bridges and railway tracks. Convection is part of many natural processes. Some of these are described below. Convection in the atmosphere plays an essential role in determining climate patterns and daily weather variations. An example of this is the blowing of land breeze and sea breeze in coastal areas. During daytime coastal land heats the air more than the sea. This hot air rises due to its less density and denser cold air from sea rushes in to take its place. Wind blows towards land due to this convection current. This is called sea breeze. At night, the land cools the air more than the sea. Hot air above the surface of sea rises. Cold air from land moves towards sea to take its place. This is called land breeze. The same principle applies in the blowing of winds. Different areas on the surface of the Earth get heated at different rates. Hot air from an area rises and cold air from other areas rushes in to take its place. Thus, a convection current is set up and this is how winds blow. The way 126 Teacher Resource Pack Guide Science 7 birds use convection to glide (remain in air without applying any force) in the sky is a very interesting natural phenomenon. The surface of the Earth warms up unequally by solar radiation. This unequal heating leads to warming of air at some places. This warm air rises due to convection. Cold air takes its place and hence a Convection Current is set up. This convection current has its special name called thermal. Birds spread their wings and use these thermals to lift themselves up. That is how they glide in air for hours. Just as convection forms thermals in air, it forms ocean currents under water. Ocean currents are an example of convection currents in liquids. Winds blowing on the surface of the ocean displace the surface water. In some places under the surface of the ocean, the water is warm. Warm water under the surface water rises and cold water rushes in to take its place. This is how convection forms currents of water in the ocean. An example is the Gulf Stream-North Atlantic-Norway Current. It starts from the North Atlantic Ocean and moves through the Arctic Ocean all the way to North Pacific Ocean. Gases at the center or core of the Sun get extremely hot and rise to the surface. Gases outside the core are not as hot so they rush inwards to replace the hotter gases from the core. Gases at the center or core of the Sun get extremely hot and rise to the surface. Gases outside the core are not as hot so they rush inwards to replace the hotter gases from the core. Life on Earth is possible because of solar energy in the form of heat. This solar energy is delivered to our planet by the process of radiation. As stated earlier, electromagnetic waves can carry not only light but also heat through vacuum. Without radiation, Earth would be subjected to an eternal winter and life would not exist. Some animals such as boas, pythons, pit vipers, piranhas and goldfish have evolved thermal vision. It means that they can see in pitch dark as well. This is because radiations from hot bodies that deliver heat to us are visible to them. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like: 4. What is thermal expansion? What is it dangerous? 5. What is the reason behind land and sea breeze, winds, ocean currents, and gliding? 6. Tell two natural processes in which radiation plays a part. Lesson 6 Topic: (8.4: Everyday applications of conduction, convection and radiation) Teaching objectives: ⦁ Recall conduction, convection and radiation. ⦁ Explain every application with relation to the mode of heat transfer. Key vocabulary: Utensil, solder, glazed, polystyrene, mat, ladle, greenhouse. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce and explain that not only does heat transfer occur in the environment but also it can be used by men in many applications. At this level, students have no prior knowledge of these applications. Now, they will be introduced to them for the first time. Introduction: Ask the students: Why do we use metal pots to cook? Why are the handles of these pots not made of metal? Why is an AC mounted on top of a wall? Write the responses on writing board. Tell the students that today we will be learning how heat transfer is used in many manmade devices. (The teacher will announce that today we are going to topic 8.4 from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that the phenomenon of transfer of heat is a blessing for humans. We apply convection, convection and radiation in useful ways to make everyday life easier and more comfortable. In this section we will discuss some applications of transfer of heat which are so useful that they have become necessities of life. Cooking pots, saucepans and boilers that are used in 127 Teacher Resource Pack Guide Science 7 cooking and heating food are made of good conductors such as metals like iron, steel etc. Tip of a solder iron is made of copper which is a good conductor of heat. This is used in soldering (reconnecting broken paths of electricity in circuits). The handles of cooking utensils mentioned above are always made of insulators such as wood and plastic. These insulators prevent burning of hands because they conduct heat very slowly. Table mats are made of a wooden material called cork. The heat of the coffee cup placed on a table mat does not reach the glass. Wooden ladles used in stirring and scooping food are made of wood which is an insulator and prevents burning. The most obvious application of insulators is in woolen clothes. Wool is an insulator so it keeps the warmth of the body inside and does not let the body heat flow to the environment. Air is also an insulator because it is a gas. This ability of air is used in double glazed windows. Air is kept in the space between the two layers of glass of the window. Polystyrene foam is a very good insulator. That is why food items and heat sensitive goods are transported after packing them in polystyrene foam. The freezing unit of a refrigerator is fixed in its top half. This helps the colder air at the top to sink and allows the warmer air at the bottom to rise. Thus, a convection current is set up which keeps the foods and beverages cool. An air conditioner works according to the same principle. Air conditioners set up convection currents in the room. Cool air from the air conditioner sinks and warm air below it rises to take its place. The heating coil of an electric kettle is fixed under the metal plate at its bottom. Water at the bottom is heated and gets lighter. It rises up while the cold water sinks to take its place. Heat is necessary for plants to grow. This heat is provided by the radiation of the sun. In cold countries, greenhouses are used to cultivate plants. Its glass walls and roof trap the heat carrying radiation inside. In this way the temperature inside the greenhouse remains high which is helpful for the plants to grow. Teapots are made of smooth, shiny materials. Shiny surfaces are good reflectors but bad emitters. Hence, teapots preserve the hotness of tea by preventing emission of radiation. Solution to Closed Book Mystery: Because the convection current is set up. Cold air from the AC at the top sinks while hot air rises to take its place. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like: 1. What is thermal expansion? How is it useful? 2. What is the principle of an AC and a refrigerator? 3. What does a greenhouse do? Lesson 7 Topic: (8.5: Vacuum Flask) Teaching objectives: ⦁ Recall conduction, convection, radiation and evaporation. ⦁ Relate the previous knowledge of vacuum and double glazing with the working of vacuum flask. Key vocabulary: Flask, thermos, evaporation, stopper, silvered. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce and explain the vacuum flask as the device which stops heat transfer by all modes that is conduction, convection and radiation. At this level, students have no prior knowledge of this application. Now, they will be introduced to it for the first time. Introduction: Ask the students: Why does your water remain cool in your water bottle? Write the responses on writing board. Tell the students that today we will be learning how heat transfer is stopped in a vacuum flask. (The teacher will announce that today we are going to topic 8.5 from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain students that a vacuum flask or thermos flask is a very interesting application of transfer of heat. It is made in such a way as to minimize heat flow from 128 Teacher Resource Pack Guide Science 7 a liquid due to all modes of transfer of heat (that is, conduction, convection and radiation) and also evaporation. A vacuum flask contains: An outer case made of shiny plastic, an inner double-glass bottle with vacuum in between the silvered glasses from the inside. A hollow plastic stopper inside the flask’s cap. Hot liquid is poured inside with trapped air between the liquid surface and the stopper. The stopper’s plastic is a poor conductor and prevents conduction from the top. The air trapped inside also prevents conduction. The vacuum between the layers of the double-glass bottle stops both conduction and convection. Silvered walls of the glass bottle reflect heat carrying radiation back to the liquid. Otherwise, radiation would travel through vacuum and carry heat away from the liquid. Evaporation (escape of liquid from the surface) only occurs when the plastic stopper is removed. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like: 4. What is vacuum? How is double glazing? 5. What is the purpose of a stopper in a vacuum flask? Review Exercise A. 1. Choose the correct answer and fill the circle. To reverse the flow of heat one must: put the hot body close to the cold body keep both bodies hot keep both bodies cold provide energy to the cold body 2. After the transfer of heat from the hot body to cold body, the cold body: gets warmer than the hot body gets colder than the hot body does not absorb heat at all becomes equal in temperature to the hot body 3. A metal pot of water is being heated on a stove. Which of the following processes is NOT happening? conduction convection radiation evaporation 4. Which of the following options correctly relates the mode of transfer of heat with the natural process? conduction, greenhouse effect convection, Solar Energy through vacuum radiation, Winds convection, ocean currents 5. Which of the following processes result from convection? gliding of birds gliding of pilots both of these expansion of concrete 6. Body A is black and body B is shiny. Both are placed near a fire. Which statement is true? body A will get heated quickly body B will get heated quickly both are heated quickly none of them 7. During a convection current, which of the following does not happen? hot air sinks hot air rises cold air sinks particles move 8. Which of the following is the most suitable for making ladles? wool copper wood iron 9. A vacuum flask prevents: conduction convection radiation all of these 10. A vacuum flask of hot liquid is opened on top of an icy mountain. Which one of the following will happen? evaporation and conduction Evaporation and convection convection only evaporation only B. Answer the following questions briefly. 1. Why does heat flow from a hot body to cold body? Ans: Hot body has more thermal energy and it is hot because it is at high temperature (degree of hotness). On the other hand, a cold body possesses low temperature. When hot and 129 Teacher Resource Pack Guide Ans: Science 7 cold bodies are brought closer to each other, the hot body transfers some of its thermal energy to the cold one. This transfer of thermal energy is called the flow of heat. 2. How does a solid conduct heat? Ans: In solids, the particles are fixed in their places under the influence of strong attractive forces. Particles of a solid can only vibrate about their fixed positions. So, during conduction of heat in a solid the particles that have more thermal energy (particles of hotter region) share it with the nearby particles of low thermal energy (particles of colder region). 3. What causes a convection-current? Ans: The convection current usually flows in a circle in the upward direction. That is because the hotter particles of the medium (liquid or gas) become lighter and rise while the heavier colder particles sink. 4. How is radiation responsible for heat transfer through vacuum? Ans: Heat does flow through vacuum and the mode of transfer is radiation. The name “Radiation” is after the waves which can carry energy (in the form of light and heat) through vacuum. These waves are called electromagnetic radiation. 5. How do birds glide for hours? Ans: The surface of the Earth warms up unequally by solar radiation. This unequal heating leads to warming of air at some places. This warm air rises due to convection. Cold air takes its place and hence convection current is set up. This convection current has its special name called thermal. Birds spread their wings and use these thermals to lift themselves up. That is how they glide in air for hours. 6. How is conduction applied in an electric iron? Ans: Electric iron is made up of solid metal which gets hot quickly due to conduction. This is how conduction heats an electric iron. 7. How does a convection-current form in an electric kettle? Ans: The heating coil of an electric kettle is fixed under the metal plate at its bottom. Water at the bottom is heated and gets lighter. It rises up while the cold water sinks to take its place. 8. How are insulators different from conductors? Ans: Among solids, some conduct heat very quickly. They are called good conductors. For example, metals such as iron and steel get hot very quickly. Solid materials such as wood, plastic etc. (nonmetals in general) conduct heat very slowly. They are called bad conductors or insulators. 9. Why does a vacuum flask contain double layered glass bottle? Ans: The vacuum between the layers of the double-glass bottle stops both conduction and convection. 10. What purpose does the trapped air in a vacuum flask serve? Ans: The air trapped inside prevents conduction. C. Answer the following questions in details. 1. Explain the flow of heat between two bodies by drawing a diagram. We sense hotness and coldness in daily life. Some objects are hot such as a hot cup of tea. Others are cold such as a cold drink of coke. An important point to remember here is that a hot body does not have more heat. It has more thermal energy and it is hot because it is at high temperature (degree of hotness). On the other hand, a cold body possesses low temperature. 130 Teacher Resource Pack Guide Science 7 Explanation: When hot and cold bodies are brought closer to each other, the hot body transfers some of its thermal energy to the cold one. In this way, the thermal energy and temperature of the hot body decrease and it cools down. The thermal energy and temperature of the cold body increase and it heats up. This transfer of thermal energy is called the flow of heat. So, heat is thermal energy in transit. The flow of heat continues till the thermal energies of both the bodies become the same. “Heat flows from a hot body to a cold body.” 2. Write a detailed note on the differences between conduction, convection and radiation. Ans: The way in which flow of heat takes place depends on what states of matter the hot body and cold body are made of. As a result, there are three modes of flow of heat. Conduction Convection Radiation The first type of modes of flow of heat is conduction. It takes place in solids. In solids, the particles are fixed in their places under the influence of strong attractive forces. Particles of a solid can only vibrate about their fixed positions. So, during conduction of heat in a solid the particles that have more thermal energy (particles of hotter region) share it with the nearby particles of low thermal energy (particles of colder region). The point to remember here is that the particles of the conductor i.e. solid (or medium) only share their thermal energy. They do not move from hot to cold region themselves. Hence, conduction can be defined as, “The process of flow of heat without the flow of the particles of the medium is called conduction.” The states of matter other than solids are liquids and gases. In liquids, atoms are still close to each other but they can move with more freedom than in solids. Particles of a gas are totally free and have large spaces between one another. They move randomly. As a result, conduction is no longer an efficient mode of flow of heat in liquids and gases. Therefore, heat flows in liquids and gases by convection. During convection not only the thermal energy of the particles but also the particles themselves move or flow from the hotter region to the colder region. This flow of particles during convection is called a convection-current. Hence, we can define convection as, “Flow of heat by the flow of the particles of the medium from hotter to colder region is called convection.” The convection current usually flows in a circle in the upward direction. That is because the hotter particles of the medium (liquid or gas) become lighter and rise while the heavier colder particles sink. The absence of any medium (solid, liquid or gas) is called vacuum. Heat does flow through vacuum and the mode of transfer is radiation. The name “Radiation” is after the waves which can carry energy (in the form of light and heat) through vacuum. These waves are called electromagnetic radiation. So, we can define radiation as, “The mode of flow of heat through vacuum with the help of electromagnetic waves is called radiation.” 3. Explain how heat transfer takes place in the environment with examples. Ans: Modes of flow of heat occur in nature and affect the environment. Let us begin with conduction. Conduction can be dangerous for buildings and structures made of solids. Not only do solids conduct heat but also expand due to rise in their thermal energy. To avoid cracking due to expansion, empty spaces are left between slabs of construction materials such as concrete, asphalt etc. The same precaution is taken during building bridges and railway tracks. Convection in the atmosphere plays an essential role in determining climate patterns and daily weather variations. An example of this is the blowing of land breeze and sea breeze in coastal areas. During daytime coastal land heats the air more than the sea. This hot air rises due to its less density and denser cold air from sea rushes in to take its place. Wind blows towards land due to this convection current. This is called sea breeze. At night, the land cools the air more than the sea. Hot air above the surface of sea rises. Cold air from land moves towards sea to take its place. This is called land breeze. The same principle applies in the blowing of winds. Different areas on the surface of the Earth get heated at different rates. Hot air from an area rises and cold air from other areas rushes in to take its place. Thus, a convection-current is set up and this is how winds blow. The way birds use convection to 131 Teacher Resource Pack Guide Science 7 glide (remain in air without applying any force) in the sky is a very interesting natural phenomenon. The surface of the Earth warms up unequally by solar radiation. This unequal heating leads to warming of air at some places. This warm air rises due to convection. Cold air takes its place and hence a Convection Current is set up. This convection current has its special name called thermal. Birds spread their wings and use these thermals to lift themselves up. That is how they glide in air for hours. Just as convection forms thermals in air, it forms ocean currents under water. Ocean currents are an example of convection currents in liquids. Winds blowing on the surface of the ocean displace the surface water. In some places under the surface of the ocean, the water is warm. Warm water under the surface water rises and cold water rushes in to take its place. This is how convection forms currents of water in the ocean. An example is the Gulf Stream-North Atlantic-Norway Current. It starts from the North Atlantic Ocean and moves through the Arctic Ocean all the way to North Pacific Ocean. Gases at the center or core of the Sun get extremely hot and rise to the surface. Gases outside the core are not as hot so they rush inwards to replace the hotter gases from the core. Radiation is as important in nature as are conduction and convection. Life on Earth is possible because of solar energy in the form of heat. This solar energy is delivered to our planet by the process of radiation. As stated earlier, electromagnetic waves can carry not only light but also heat through vacuum. Without radiation, Earth would be subjected to an eternal winter and life would not exist. Some animals such as boas, pythons, pit vipers, piranhas and goldfish have evolved thermal vision. It means that they can see in pitch dark as well. This is because radiations from hot bodies that deliver heat to us are visible to them. 4. Differentiate between the working of conductors and insulators. Ans: Among solids, some conduct heat very quickly. They are called good conductors. For example, metals such as iron and steel get hot very quickly. Solid materials s uch as wood, plastic etc. (non-metals in general) conduct heat very slowly. They are called bad conductors or insulators. 5. Write a detailed note on a vacuum flask. Ans: A vacuum flask contains: An outer case made of shiny plastic An inner double-glass bottle with vacuum in between the silvered glasses from the inside A hollow plastic stopper inside the flask’s cap Working: Hot liquid is poured inside with trapped air between the liquid surface and the stopper. The stopper’s plastic is a poor conductor and prevents conduction from the top. The air trapped inside also prevents conduction. The vacuum between the layers of the double-glass bottle stops both conduction and convection. Silvered walls of the glass bottle reflect heat carrying radiation back to the liquid. Otherwise, radiation would travel through vacuum and carry heat away from the liquid. Evaporation (escape of liquid from the surface) only occurs when the plastic stopper is removed. D. Thought Experiment. 1. You are to heat water without any heat source except sunlight. Which of the following types of materials would you choose for your container? Also state the reasons for your choice. a. Shiny or Dull. Dull because it absorbs more heat b. Rough or Smooth. Rough because it absorbs more heat c. Bright or Dark. Dark because it absorbs more heat Unit # 9 DISPERSION OF LIGHT Lesson 1 132 Teacher Resource Pack Guide Science 7 Topic: (9.1: Refraction) Teaching objectives: ⦁ Recall energy and work. ⦁ Recall light as energy. ⦁ Recall rays of light. ⦁ Recall reflection of light. ⦁ Introduce refraction of light. ⦁ Explain the refraction in different media. Key vocabulary: Energy, work, light, ray, bend, refract, medium, incidence, refraction, angle. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this unit is to revise light and introduce the refraction of light. It will help the students to understand how and when light bends. At this level, students have prior knowledge of refraction of light. Now, they will be introduced to this process in detail. Introduction: Ask the students: Why does a pencil bend in a glass of water? Write the responses on writing board. Tell the students that today we will be learning what causes light to bend. (The teacher will announce that today we are going to begin 9th chapter from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that from previous knowledge, we know that light is a form of energy that travels in straight lines called rays. We are also familiar with reflection of light and the laws of reflection. In this chapter, we shall study another natural phenomenon that concerns light. It is called refraction. In simple words, light bends when it changes medium. The teacher will ask the students that have you ever observed the apparent bending of a pencil when it is immersed in a glass of water? It is due to refraction. As mentioned earlier, light travels in straight lines called rays. During this travel, light rays come across surfaces at which the medium changes. For example, when a light ray from air enters another medium (glass or water) at an angle, it bends after entering. Similarly, when the ray exits the medium and enters air, it bends again. This bending is called refraction of light. “Bending of rays of light due to change in medium is called refraction.” Refraction is caused due to difference in speeds of light in different media. In air light travels with a speed of about 3x108 meters per second. When light travels into a medium that is denser (with more mass per unit volume) than air, its speed of travel decreases by a slight amount due to which the ray of light bends. During refraction, light ray bends due to change in medium because it travels at different speeds in the two media. Let us define these two media and some related concepts before we get to understand how refraction takes place in different media. An optically rare medium (or simply rare medium such as air) is one in which light travels faster. An optically denser medium (or simply denser medium such as glass or water) is one in which light travels a bit slower. The ray before bending is called the incident ray. After refraction, it is named the refracted ray. The normal is an imaginary perpendicular line through the denser medium. The angle between the incident ray and the normal is called the angle of incidence (i). The angle between the refracted ray and the normal is called the angle of refraction (r). If a ray of light from a rare medium (air) enters the denser medium (glass or water) at an angle, it bends towards the normal. When it travels from a denser medium to a rare medium, it bends away from the normal. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is work? What is energy? 2. Is light energy? What is a ray? 3. What is reflection? What is refraction? 4. How does it happen? Lesson 2 Topic: Teaching objectives: 133 (9.2: Laws of Refraction) ⦁ Recall refraction of light. ⦁ Explain the laws of refraction. Teacher Resource Pack Guide Science 7 Key vocabulary: Energy, work, light, ray, bend, refract, medium, incidence, refraction, angle, normal, Snell’s law, sine. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Scientific Calculator for worked example Background: The purpose of this topic is to revise the laws of refraction. It will help the students to understand that these laws govern the process of refraction. At this level, students have prior knowledge of these laws. Now, they will learn to apply them. Introduction: Ask the students: Take out their calculators and locate the sin button. Tell the students that today we will be learning the laws of refraction by using a mathematical formula. (The teacher will announce that today we are going to begin topic 9.2 from 9th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that just as nature has determined the rules or laws of reflection, it has determined the laws of refraction. These are the rules according to which refraction of light takes place. The two laws of refraction are described as follows. First law of Refraction states that, “The incident ray, the refracted ray, and the normal, all lie on the same plane.” Second law of Refraction or Snell’s Law states that, “For two particular media (say air and glass) the ratio of the sine of angle of incidence to the sine of angle of refraction remains constant.” sin 𝑖 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 sin 𝑟 To explain the application of Snell’s law follow worked example 9.1 on page 118 of the book. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is refraction? How does it happen? 2. Define first law of refraction. Define Snell’s law. 3. State the mathematical formula of Snell’s law. Lesson 3 Topic: (9.2.3: Refractive Index) Teaching objectives: ⦁ Recall refraction of light. ⦁ Recall the laws of refraction. ⦁ Explain the formula of Snell’s law. ⦁ Identify the formula as Refractive Index. ⦁ Symbolize refractive index by ‘n’. ⦁ Give the refractive index formula of ratio of speeds of light invacuum and medium. Key vocabulary: Energy, work, light, ray, bend, refract, medium, vacuum, incidence, refraction, angle, normal, Snell’s law, sine, refractive index, speed of light. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Scientific Calculator for worked example Background: The purpose of this topic is to identify refractive index formula with that of Snell’s law. It will help the students to understand that refractive index gives a measure of the bending of light during refraction. At this level, students have no prior knowledge of refractive index. Now, they will be introduced to it for the first time. Introduction: Ask the students: Take out their calculators and locate the sin button. Tell the students about the power button and how to write a value as powers of ten. Tell them that today we will be learning about refractive index and speed of light in different media. (The teacher will announce that today we are going to begin topic 9.2.3 from 9th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) 134 Teacher Resource Pack Guide Science 7 Explanation: Now, teacher will explain to the students that it has been stated earlier that light bends when it moves from a rare medium to a denser medium. This is because in the denser medium the speed of light reduces slightly. Also, the second law of refraction dictates that the ratio of the sines of angles of incidence and refraction remains constant for two particular media (Snell’s law). So, these two seemingly different observations explain the same phenomenon, that is, refraction of light. This implies that there must be a link between these two observations. Indeed, they are two different ways of expressing Snell’s law. Suppose that speed of light in vacuum (which is exactly 3x108 meters per second) is symbolized by “c” and speed of light in a (denser) medium by “v”. Then, “The ratio of speed of light in vacuum to speed of light in medium is called the refractive index of that medium (n).” 𝑐 𝑛= 𝑣 The refractive index for common materials is always positive. It tells us the amount of bending of light by a medium in numbers. For a particular medium, the refractive index remains the same for all angles of incidence and refraction. So we can generalize the second law of refraction as, 𝑐 sin 𝑖 𝑛= = 𝑣 sin 𝑟 Explain table 9.1 on page 119 to help the students realize the refractive indices and speeds of light in different media. To help them apply the formula of refractive index, guide them through worked example 9.2 on page 119. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 4. What is speed of light in vacuum and medium? 5. What is refractive index? 6. State the mathematical formula of refractive index. 7. Relate the mathematical formula of refractive index with that of Snell’s law. 8. Tell the refractive indices of different materials. Lesson 4 Topic: (9.3: Effects of Refraction) Teaching objectives: ⦁ Recall refraction of light. ⦁ Recall the laws of refraction. ⦁ Recall the formula of Snell’s law. ⦁ Introduce natural processes that are the effects of refraction. Key vocabulary: Real, apparent, depth, fish eye, mirage Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to understand those natural processes which are caused by refraction. It will help the students to understand that refraction occurs in nature as well and it produces illusions. At this level, students have no prior knowledge of these phenomena. Now, they will be introduced to them for the first time. Introduction: Ask the students: Why does the depth of a swimming pool full of water appears less when seen from above? Write their responses on the board. Tell them that today we will be learning about different natural effects of refraction. (The teacher will announce that today we are going to begin topic 9.3 from 9th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that a swimming pool appears less deep when seen from above at an angle. This is because of refraction. Light rays from objects underwater reach our 135 Teacher Resource Pack Guide Science 7 eyes after refraction. This bending of rays from their original path makes the depth appear less. The actual depth of the body of water (pool, lake or any other) is called real depth. The depth which appears less due to refraction is called apparent depth. Another example is fish eye view. To avoid visual distortion due to refraction an archer fish always positions itself directly under the prey (bug). Then it squirts a stream of water which hits the prey and it falls into water to be eaten. Sometimes an archer fish avoids visual distortion by instinct. It adjusts the squirt according to the amount of refraction. A mirage is a natural phenomenon in which light rays bend to produce a displaced image of distant objects or the sky. Mirages are of different types. During a heat haze, light rays coming from a particular distant object travel through nearly the same of layers. So, they are bent over about the same amount. The image usually is upside down. A mirage of an astronomical object is one in which light rays are bent to produce distorted or multiple images of an astronomical object. This is observed at night. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. Name the effects of refraction. 2. What is the difference between real and apparent depth? 3. How does fish eye view work? What is a mirage? Lesson 5 Topic: (9.4: Dispersion of Light) (9.4.1: Spectrum and Rainbow) Teaching objectives: ⦁ Recall refraction of light. ⦁ Recall the laws of refraction. ⦁ Introduce prism. ⦁ Introduce and explain dispersion of light. ⦁ Introduce spectrum and rainbow and explain them. Key vocabulary: Prism, dispersion, spectrum, violet, indigo, rainfall, droplets, disperse, scatter, spread. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. A compact disc mounted on a rod and motor for classroom activity Background: The purpose of this topic is to introduce the dispersion of light. It will help the students to understand that light is made of seven colours and that dispersion is a natural process in which light. At this level, students have no prior knowledge of these phenomena. Now, they will be introduced to them for the first time. Introduction: Ask the students: Why does a CD change colour when it is moved around in light? Write their responses on the board. Tell them that today we will be learning about the dispersion of light into its seven component colours. (The teacher will announce that today we are going to begin topic 9.4 from 9th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that a prism is an optical object with transparent, flat and polished surfaces that refract light. At least two of the flat surfaces have an angle between them. Prisms are responsible for an interesting phenomenon called dispersion of light. Visible light (or white light) is made up of seven colour: violet, indigo, blue, green, yellow, orange and red. When a ray of white light strikes a refracting surface of the prism, it is split into rays of its constituent colours. “Splitting of light into its component colours by refracting surfaces is called dispersion.” Dispersion occurs because the ray of every component colour of white light has different characteristics. Upon entering a denser medium they bend by different amounts. White light consists of seven colours. These seven colours, together, are called Spectrum (or optical spectrum to be more specific). “Seven colours of light make up the spectrum.” Rainbow is also a consequence of refraction of light. It is usually visible in the sky after rainfall. After rainfall, tiny droplets of water present in the air refract light like a prism. Rays of white light are dispersed into its seven component colours. Classroom Activity (Page 121 on book): To explain to the students that white light is made of 136 Teacher Resource Pack Guide Science 7 seven colours follow the activity on page 121 of the book. Hold the disc and move it around against incident light. You will see different colours after in it. Now, mount the disc on the axle of the rotor. Turn the rotor (a motor with an axle) on. The disc will start spinning. At first the disc will show colours. Increase the spinning speed of the rotor gradually. When the disc gains high speed, colours will disappear. At high speed, the spinning disc will appear white. Answer: It is because white light contains seven colours. At high speed these colours mix to give white colour. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. How many colours are there in white light? Name the seven colours in order. 2. What is a prism? What is the dispersion of light? 3. What is a spectrum? Why do we see a rainbow after rainfall? 4. Lesson 6 Topic: (9.4.2: Colours) (9.4.3: Uses of Colours and Coloured Lights) (9.4.4: Three chip video camera) Teaching objectives: ⦁ Recall light. ⦁ Recall opaque. ⦁ Recall colour. ⦁ Introduce primary colours. ⦁ Introduce secondary colours. ⦁ Explain uses of colours and coloured lights. Key vocabulary: Opaque, luminous, nonluminous, opaque, colour, primary, secondary, traffic, advertise, publicity, décor, three chip. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Red, blue and yellow paints for classroom activity. Background: The purpose of this topic is to introduce the colours and their types. It will help the students to understand that opaque objects give colours. At this level, students have some prior knowledge of colour. Now, they will be introduced to primary and secondary colours for the first time. Introduction: Ask the students: Draw yellow colour on a paper first and then blue colour on top of the yellow. What happens? Write their responses on the board. Tell them that today we will be learning about colours, their mixing and their uses. (The teacher will announce that today we are going to begin topic 9.4.2 from 9th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students in previous classes we divided objects into two kinds: luminous and non-luminous. Luminous objects produce their own light while non-luminous objects only reflect or absorb light from luminous objects. We also classified surfaces as transparent, opaque and translucent. Unlike transparent and translucent surfaces, opaque surfaces reflect and absorb light totally. Due to this reflection and absorption, we see opaque objects as coloured. The colour of an object is that portion of light which it does not absorb but reflects. “Colour of an opaque object is that component portion of white light which it reflects.” Among colours some are primary while others are secondary. Primary colours are those which cannot be made by the mixing of other colours. The three primary colours are red, blue and yellow. Secondary colours are those which can be made by mixing of primary colours. For example, if we mix yellow and blue, we get green. Purple and orange are formed by mixing blue and red, and yellow and red respectively. On the streets, colour is used not just for light but also as a sign itself. For example red is used on prohibitive road signs - No Entry etc. Neon signs in different colours are used for 137 Teacher Resource Pack Guide Science 7 advertisement purposes as they are bright and flashy. Red also appears as the colour of car brake lights. It also alerts the drivers following us. Red also has the effect of awareness. It is the colour for stop. This is ideal when there is potential danger. Night lights in bedrooms are made coloured to reduce brightness during sleeping hours. In décor colour will create an atmosphere, in a public space that is to say or do something to others. For example green in the hospital ward, yellow in the kindergarten. The full-colour image seen by a professional video camera goes through a beam-splitter (on the right half of the drawing) that separates the full-color picture into its red, green and blue components. For example, all of red light, blue light and green light in a colour scene is split by a colour-selecting mirror and then sent to the respective receptors. Thus, what was a full-colour picture is now been separated into the percentages of red, green and blue light contained in the original scene. Classroom Activity (Page 122 on book): To explain to the students the primary and secondary colours, follow the activity on page 122 of the book. Mix blue and red paints. Then mix blue and yellow paints. Then mix red and yellow paints. Answer: Red, blue and yellow are primary colours. The following colours are produced in each case: Blue + Red = Purple Blue + Yellow = Green Red + Yellow = Orange Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. How many colours are there in white light? Name the seven colours in order. 2. What are primary colours? What are secondary colours? 3. Name primary and secondary colours. How does a three chip camera work? Test Exercise – 1 A. 1. Choose the correct answer and fill the circle. Bending of light due to change of medium is called: reflection refraction conduction convection 2. The medium in which light travels at lower speed is called: rare medium denser medium liquid gas 3. The refractive index of ice is: 2.2 2.3 1.3 1.0 4. Speed of light in vacuum is: 2 × 108 meters per second 4 × 108 meters per second 8 1 × 10 meters per second 3 × 108 meters per second 5. Colour is that portion of light which an opaque object: reflects refracts absorbs disperses B. Answer the following questions briefly. 1. What does it mean by refraction? Ans: Bending of light due to change in medium is called refraction. 2. Describe the hunting method of an archer fish. Ans: To avoid visual distortion due to refraction, an archer fish always positions itself directly under the prey (bug). Then it squirts a stream of water which hits the prey and it falls into water to be eaten. Sometimes an archer fish avoids visual distortion by instinct. It adjusts the squirt according to the amount of refraction. 3. Write down the names of colours of light dispersed by a prism in the correct order. Ans: Violet, indigo, blue, green, yellow, orange, red. 4. Differentiate between primary and secondary colours with an example. Ans: Primary colours are those which cannot be made by the mixing of other colours. The three primary colours are red, blue and yellow. Secondary colours are those which can be made by 138 Teacher Resource Pack Guide Science 7 mixing of primary colours. For example, if we mix yellow and blue, we get green. Lesson 7 Topic: (9.5: Total Internal Reflection) Teaching objectives: ⦁ Recall reflection. ⦁ Recall the laws of reflection. ⦁ Introduce total internal reflection. ⦁ Introduce critical angle. ⦁ Introduce secondary colours. ⦁ Explain uses of colours and coloured lights. Key vocabulary: Reflection, total, internal, critical, angle, denser, rare. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Semicircular glass slab, slit, paper, pencil, and protractor for classroom activity. Background: The purpose of this topic is to introduce the total internal reflection and critical angle. It will help the students to understand that light can be totally reflected inside the denser medium. At this level, students have no prior knowledge of this process. Now, they will be introduced to it for the first time. Introduction: Ask the students: See the image of a pencil from under the surface of water in a glass. What do you see? Write their responses on the board. Tell them that today we will be learning about this process called total internal reflection. (The teacher will announce that today we are going to begin topic 9.5 from 9 th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that they partially fill a transparent bottle with water. Hold a laser-light outside the glass and under the surface of water. Point it at an angle towards the surface of water from below. Slowly move the laser-light. You will observe that at a certain position, the laser-light does not exit the water surface by refraction. It is reflected back inwards. This phenomenon is called the total internal reflection of light. “Complete, inward reflection of a ray of light by the boundary of a denser medium is called total internal reflection.” The denser medium may be water, glass, ice, diamond etc. Total internal reflection does not occur at all angles. For a particular denser medium, it happens after a particular angle called the critical angle. At the critical angle, the ray becomes parallel to the refracting surface. Below this angle, light is only partially reflected by the boundary. Rest of the light is refracted into the rare medium (air). The determination of critical angle is described by the following activity. Classroom Activity (Page 125 on book): To explain to the students the calculation of critical angle, follow the activity on page 125 of the book. Place the semicircular glass slab on the paper and draw its outline. Draw the normal (which passes through) on the flat edge of the outline. Now place the slit at the center of the circular face. The beam of sunlight will pass straight through. Now start moving it towards the corner of the slab. Observe the behaviour of light inside glass. At a certain point all the light will be reflected inward by the flat face inside the glass. Mark the position of the sunlight B on the paper and join it with point A. Measure the angle between the normal and the line joining A to B by the protractor. This gives the approximate value of the critical angle. Answer: Critical angle is that particular angle below which total internal reflection cannot occur. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. Define reflection. Define total internal reflection. 2. Define critical angle. Lesson 8 Topic: (9.6: Applications of Total Internal Reflection) Teaching objectives: ⦁ Recall reflection. ⦁ Recall the laws of reflection. ⦁ Recall total internal reflection. ⦁ Recall critical angle. 139 Teacher Resource Pack Guide Science 7 ⦁ Introduce reflecting prism. ⦁ Introduce prism based periscope. Key vocabulary: Reflection, total, internal, critical, angle, denser, rare, prism, periscope, prism based. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce the applications of total internal reflection. It will help the students to understand that total internal reflection can be used in devices as well. At this level, students have no prior knowledge of these applications. Now, they will be introduced to them for the first time. Introduction: Ask the students: Recall a periscope. What does it do? Write their responses on the board. Tell them that today we will be learning about reflecting prisms and prism based periscope. (The teacher will announce that today we are going to begin topic 9.6 from 9th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that like reflection, refraction and dispersion, total internal reflection is also utilized in making devices that serve different purposes. Following are some applications of total internal reflection. A prism which can totally reflect light internally is called a reflecting prism. The condition for total internal reflection in such a prism is that the ray which strikes the internal reflecting surface must make an angle with the normal that is higher than the critical angle of glass used in that prism. Periscope is a device which is used to see above high obstacles (or above water surface from a submarine). We are already familiar with the design of a periscope that uses mirror strips. But its aluminum coated mirrors rust when used in water. This causes the blurring of image. The prism based periscope is more efficient. Not only does it produce a clear and magnified image (when includes a lens) but also its glass prisms do not rust like aluminum coated mirrors used in a mirror based periscope. Submarines and tanks use prism based periscopes. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 3. Define reflection. Define total internal reflection. 4. Define critical angle. What is a reflecting prism? 5. What is a periscope? 6. Why a prism-based periscope is better than a mirror based periscope? Review Exercise A. 1. 2. 3. 4. 5. Choose the correct answer and fill the circle: A denser medium refracts light because: light changes colour in the denser medium light stops in the denser medium light changes speed in the denser medium light is converted into sound Which of the following statements about mirages is correct? they are caused by reflection of light a mirage is seen only during day during a heat haze the image is usually upside down a mirage is only seen by a person who is mentally ill Which of the following colours is not a part of the spectrum of light? blue orange grey green Dispersion through a prism occurs because: the prism is faulty the prism produces the colours by itself white light is made of component colours original light is destroyed and then colours are created Which of the following combinations represents primary colours? 140 Teacher Resource Pack Guide red, yellow, blue Science 7 red, purple, blue red, green, blue red, orange, green 6. Rainbow in the sky is caused by: prism winds lightening water droplets 7. An opaque object is coloured because of: absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one 8. Total internal reflection occurs: at critical angle after critical angle at the normal in the rare medium 9. The principle of a reflecting prism is: reflection refraction total internal reflection dispersion 10. A prism based periscope is better because: it produces a clear, magnified image prisms disperse light prisms do not rust like aluminum coated mirrors both first and third options. B. Answer the following questions shortly. 1. When do transparent surfaces refract light? Ans: When the speed of light in transparent media differs then refraction is caused. 2. What causes refraction? Ans: The main cause of refraction is the difference in speed of light in different media which it crosses. 3. What does the refractive index tell us? Ans: Refractive index is the measure of how much bending of light is produced by a medium. 4. How does a swimming pool appear less deep? Ans: Apparent depth of a swimming pool appears less because of refraction of light. 5. When does a prism disperse light? Ans: Visible light (or white light) is made up of seven colours: violet, indigo, blue, green, yellow, orange and red. When a ray of white light strikes a refracting surface of the prism at an angle, it is split into rays of its constituent colours. 6. Differentiate between primary and secondary colours. Ans: Primary colours are those which cannot be made by the mixing of other colours. Secondary colours are those which can be made by mixing of primary colours. 7. What separates the coloured lights in a three-chip camera? Ans: A beam-splitter (on the right half of the drawing) separates the full-color picture into its red, green and blue components. 8. When does total internal reflection occur in a prism? Ans: When the angle of incidence becomes greater than the critical angle then total internal reflection occurs. 9. Why do submarines have prism based periscopes? Ans: Because prism surfaces do not rust in water like aluminum coated mirrors. 10. What happens when the incident ray strikes exactly at critical angle? Ans: The refracted ray becomes parallel to the boundary of the denser medium. C. Answer the following questions in details. 1. Write a detailed note on refraction, its cause and its occurrence in the environment. Ans: Light travels in straight lines called rays. During this travel, light rays come across surfaces at which the medium changes. For example, when a light ray from air enters another medium (glass or water) at an angle, it bends after entering. Similarly, when the ray exits the medium and enters air, it bends again. This bending is called refraction of light. Refraction is caused due to difference in speeds 141 Teacher Resource Pack Guide Science 7 of light in different media. In air light travels with a speed of about 3x108 meters per second. When light travels into a medium that is denser (with more mass per unit volume) than air, its speed of travel decreases by a slight amount due to which the ray of light bends. An optically rare medium (or simply rare medium such as air) is one in which light travels faster. An optically denser medium (or simply denser medium such as glass or water) is one in which light travels a bit slower. The ray before bending is called the incident ray. After refraction, it is named the refracted ray. The normal is an imaginary perpendicular line through the denser medium. The angle between the incident ray and the normal is called the angle of incidence (i). The angle between the refracted ray and the normal is called the angle of refraction (r). If a ray of light from a rare medium (air) enters the denser medium (glass or water) at an angle, it bends towards the normal. When it travels from a denser medium to a rare medium, it bends away from the normal. The two laws of refraction are described as follows. First law of Refraction: The incident ray, the refracted ray, and the normal, all lie on the same plane. Second law of Refraction or Snell’s Law: For two particular media (say air and glass) the ratio of the sine of angle of incidence to the sine of angle of refraction remains constant. Effects of Refraction: Following are the effects of refraction. Real and Apparent Depth: A swimming pool appears less deep when seen from above at an angle. This is because of refraction. Light rays from objects underwater reach our eyes after refraction. This bending of rays from their original path makes the depth appear less. The actual depth of the body of water (pool, lake or any other) is called real depth. The depth which appears less due to refraction is called apparent depth. Fish Eye View: To avoid visual distortion due to refraction an archer fish always positions itself directly under the prey (bug). Then it squirts a stream of water which hits the prey and it falls into water to be eaten. Sometimes an archer fish avoids visual distortion by instinct. It adjusts the squirt according to the amount of refraction. Mirage: A mirage is a natural phenomenon in which light rays bend to produce a displaced image of distant objects or the sky. Mirages are of different types. During a heat haze, light rays coming from a particular distant object travel through nearly the same of layers. So, they are bent over about the same amount. The image usually is upside down. A mirage of an astronomical object is one in which light rays are bent to produce distorted or multiple images of an astronomical object. This is observed at night. 2. Explain with examples how refraction has made our lives easier. Ans: Application of refraction is in prisms. A prism is an optical object with transparent, flat and polished surfaces that refract light. At least two of the flat surfaces have an angle between them. Prisms are responsible for an interesting phenomenon called dispersion of light. Visible light (or white light) is made up of seven colour: violet, indigo, blue, green, yellow, orange and red. When a ray of white light strikes a refracting surface of the prism, it is split into rays of its constituent colours. This has many uses such as cameras, TVs, computers etc. 3. Write a note on refractive index and explain its mathematical formula. Ans: The second law of refraction dictates that the ratio of the sine of angles of incidence and refraction remains constant for two particular media (Snell’s law). So, these two seemingly different observations explain the same phenomenon, that is, refraction of light. This implies that there must be a link between these two observations. Indeed, they are two different ways of expressing Snell’s law. Suppose that speed of light in vacuum (which is exactly 3x108 meters per second) is symbolized by “c” and speed of light in a (denser) medium by “v”. Then, “The ratio of speed of light in vacuum to speed of light in medium is called the refractive index of that medium (n).” n=c/v 142 Teacher Resource Pack Guide Science 7 The refractive index for common materials is always positive. It tells us the amount of bending of light by a medium in numbers. For a particular medium, the refractive index remains the same for all angles of incidence and refraction. So we can generalize the second law of refraction as, n = c / v = sin i / sin r 4. Write a note on the uses of colour and coloured lights. Ans: Unlike transparent and translucent surfaces, opaque surfaces reflect and absorb light totally. Due to this reflection and absorption, we see opaque objects as coloured. The colour of an object is that portion of light which it does not absorb but reflects. “Colour of an opaque object is that component portion of white light which it reflects.” Among colours some are primary while others are secondary. Primary colours are those which cannot be made by the mixing of other colours. The three primary colours are red, blue and yellow. Secondary colours are those which can be made by mixing of primary colours. For example, if we mix yellow and blue, we get green. Purple and orange are formed by mixing blue and red, and yellow and red respectively. Uses of Colours and Coloured Lights: We use coloured lights in a variety of ways to make our lives easier. Following are some applications of coloured lights at home, school and for the country. It is an obvious use of coloured lights. Red means “Stop” as it alerts the person. Yellow means “Get ready”, and green means “Go.” On the streets, colour is used not just for light but also as a sign itself. For example red is used on prohibitive road signs - No Entry etc. Neon signs in different colours are used for advertisement purposes as they are bright and flashy. Red also appears as the colour of car brake lights. It also alerts the drivers following us. Red also has the effect of awareness. It is the colour for stop. This is ideal when there is potential danger. Night lights in bedrooms are made coloured to reduce brightness during sleeping hours. In décor colour will create an atmosphere, in a public space that is to say or do something to others. For example green in the hospital ward, yellow in the kindergarten. 5. Explain the process of total internal reflection and its uses. Ans: Complete, inward reflection of a ray of light by the boundary of a denser medium is called total internal reflection. The denser medium may be water, glass, ice, diamond etc. Total internal reflection does not occur at all angles. For a particular denser medium, it happens after a particular angle called the critical angle. At the critical angle, the ray becomes parallel to the refracting surface. Below this angle, light is only partially reflected by the boundary. Rest of the light is refracted into the rare medium (air). Like reflection, refraction and dispersion, total internal reflection is also utilized in making devices that serve different purposes. Following are some applications of total internal reflection. A prism which can totally reflect light internally is called a reflecting prism. The condition for total internal reflection in such a prism is that the ray which strikes the internal reflecting surface must make an angle with the normal that is higher than the critical angle of glass used in that prism. Periscope is a device which is used to see above high obstacles (or above water surface from a submarine). We are already familiar with the design of a periscope that uses mirror strips. But its aluminum coated mirrors rust when used in water. This causes the blurring of image. The prism based periscope is more efficient. Not only does it produce a clear and magnified image (when includes a lens) but also its glass prisms do not rust like aluminum coated mirrors used in a mirror based periscope. Submarines and tanks use prism based periscopes. Solution to Numerical with Thought Experiment: He should perform refraction of light because light will not be totally reflected back by the denser medium. We use the formula 143 Teacher Resource Pack Guide Science 7 𝑛= 𝑐 sin 𝑖 = 𝑣 sin 𝑟 First the speed of light in the medium 𝑣= 𝑣= v = 1.24 x 108 meters per second The medium is diamond. sin 𝑟 𝑐 sin 𝑖 sin 17 3 x 108 sin 45 Unit # 10 SOUND WAVES Lesson 1 Topic: (10.1: Transverse and Longitudinal Waves) Teaching objectives: ⦁ Recall energy and work. ⦁ Recall sound as energy. ⦁ Recall wave. ⦁ Recall sound waves. ⦁ Introduce transverse and longitudinal waves. ⦁ Demonstrate transverse and longitudinal waves. Key vocabulary: Energy, work, wave, sound, sound waves, transverse, longitudinal, crest, trough, compression, rarefaction. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Long slinky spring, wall, nail, hammer for classroom activity. Background: The purpose of this unit is to revise sound and to introduce the longitudinal and transverse waves. It will help the students to understand the difference between transverse and longitudinal waves. At this level, students have prior knowledge of sound waves. Now, they will be introduced to them in detail. Introduction: Ask the students: Have they ever produced waves in a pond by throwing pebbles? What did they observe? Write the responses on writing board. Tell the students that today we will be learning what is the nature of sound waves in particular. (The teacher will announce that today we are going to begin 10th chapter from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that in previous classes, we studied that energy has different forms. One of these forms is sound. Its nature is kinetic and is produced by vibrating objects. We also know that sound requires a medium for propagation (travelling). Sound travels fastest in solids, faster in liquids, and quite fast in gases. Sound energy is transported by sound waves. In this chapter we shall explore the nature of sound waves and their applications. A wave is a disturbance (may or may not be in a medium) that transports energy by its propagation. That disturbance is due to the vibration or to and fro movement of the particles of the medium. The kinetic energy of vibration is shared by the source to the particles of the medium. This sharing of energy travels to the particles that are next in line. Sharing of energy goes on and this is how a wave travels. On the basis of vibration of particles, waves can be classified into two types: 1. Transverse Waves 2. Longitudinal Waves 144 Teacher Resource Pack Guide Science 7 Transverse waves are those in which a wave moves forward but the particles vibrate up and down. These waves travel as crests (hills) and troughs (valleys). A longitudinal wave moves forward and the particles of the medium also vibrate back and forth. These waves travel as compressions (particles come close to each other) and rarefactions (particles move away from each other). Water waves are transverse waves. Sound waves are longitudinal. Their propagation depends on the presence of a medium. They cannot propagate in vacuum. Classroom Activity (Page 130 on book): To explain the difference between transverse and longitudinal waves better, follow the activity on page 130 of the book. Hammer a nail into a support such as wall. Fix one end of the spring with the nail. Lay it on a table or the floor. Take the other hand in your hand and move away from the nail until the spring gets straight. First, give up and down jerking movement to your hand holding the spring and produce waves. Now give back and forth movement to your hand and produce waves. Answers: Transverse waves are produced by up and down movement. Back and forth movement does not produce peaks and valleys. They produce compressions and rarefactions. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is energy? Is sound energy? 2. What is a wave? What are transverse and longitudinal waves? 3. What are crests and troughs? What are compressions and rarefactions? Lesson 2 Topic: (10.2: Wave Terms) Teaching objectives: ⦁ Recall energy and work. ⦁ Recall sound as energy. ⦁ Recall wave. ⦁ Recall sound waves. ⦁ Introduce transverse and longitudinal waves. ⦁ Introduce wave terms: wavelength, frequency, amplitude, time period and frequency. ⦁ Explain audible frequency range. Key vocabulary: Energy, work, wave, sound, sound waves, transverse, longitudinal, crest, trough, compression, rarefaction, wavelength, frequency, amplitude, time period, audible, range. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Calculator for worked example Background: The purpose of this unit is to introduce wave terms. It will help the students to understand the terms that characterize a wave in a quantitative manner. At this level, students have no prior knowledge of wave terms. Now, they will be introduced to them for the first time. Introduction: Tell two of the students to take a rope. Move it up and down at one end; first slowly then fast. Ask them what they observe. Write the responses on writing board. Tell the students that today we will be learning about the terms that explain this difference. (The teacher will announce that today we are going to begin topic 10.2 from the 10th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that a wave is a disturbance which carries energy. To gain knowledge of the properties and behaviour of waves, we have worked out some terms. These terms are mathematical quantities which can be calculated. Studying the following important wave terms will give you an insight about waves. We have stated that a wave travels from one place to another Transverse waves are produced by up and down vibration while sound travels as longitudinal waves (back and forth vibration). During the movement of a transverse wave some particles of the medium move up to produce peaks called crests. Other particles move down to produce valleys called troughs. The distance between two 145 Teacher Resource Pack Guide Science 7 successive crests (or troughs) is called wavelength of a transverse wave. Sound energy from a vibrating object moves the particles of the medium back and forth and a longitudinal wave is set up. Along the waves regions are produced where particles move towards each other. These regions are called compressions. The regions where particles move away from each other are called rarefactions. One compression is separated from the other by a rarefaction. This distance between two compressions (or rarefactions) is called wavelength. “The distance between the midpoints of two successive compressions (or rarefactions) is called the wavelength of a sound wave.” Sound is produced by a vibrating object. Time taken by a vibrating object to complete one back and forth vibration is called time period (T). The vibrating object and the particles of the medium vibrate with the same time period. Time period is usually calculated in seconds (s). During one time period, the wave covers a distance of one wavelength. Frequency (f) of a sound wave is the number of vibrations made by the particles of the medium in one second. Frequency is calculated in hertz (Hz). Frequency and time period are related by the formula, 1 𝑓= 𝑇 For a transverse wave, frequency and time period are calculated by the same method but for up and down movement of particles. To explain frequency and time period formula better, follow the worked example 10.1 on page 132. The word audible means “can be heard”. Audible frequency range refers to those frequencies of sound waves which humans can hear. This range lies between 20 hertz to 20,000 hertz. Other animals may have narrower or wider ranges of audible frequencies. For example, an elephant can hear in the range 17 to 11,000 hertz. So its audible frequency range is narrower than that of humans. On the other hand a cat’s hearing range is wider than that of humans (55 to 77,000 hertz). The following graph compares the audible frequency ranges of different animals. The amplitude of a transverse wave refers to the vertical distance between the mean position and a crest (or trough). In case of a sound wave (which is longitudinal) the amplitude is calculated by the variation of pressure of the medium due to compressions (high pressure regions) and rarefactions (low pressure regions). Hence, the amplitude of a sound wave can be defined as, “The maximum pressure change in the medium is the amplitude of a sound wave.” Amplitude is denoted by “A.” Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is wavelength? What is frequency? 2. What is amplitude? What is time period? 3. What is the audible frequency range for humans? Lesson 3 Topic: (10.3: Characteristics of Sound) (10.3.1: Factors that affect sound) Teaching objectives: ⦁ Recall wave terms: wavelength, frequency, amplitude, time period and frequency. ⦁ Introduce characteristics of sound: pitch and loudness. ⦁ Introduce factors that affect sound: medium, movement and area. Key vocabulary: Pitch, loudness, surface area, medium, movement, source, observer. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Six identical glass bottles, water, spoon. Background: The purpose of this unit is to introduce the characteristics of a sound wave; pitch and loudness. It will help the students to relate wave terms such as frequency and amplitude with pitch and loudness. At this level, students have no prior knowledge of these characteristics. Now, they will be introduced to them for the first time. 146 Teacher Resource Pack Guide Science 7 Introduction: Ask the students, “Why are voices of some people grave and those of others shrill?” Write the responses on writing board. Tell the students that today we will be learning about the characteristics that make different sounds. (The teacher will announce that today we are going to begin topic 10.3 from the 10th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that sounds can be pleasant or unpleasant. Pleasant sounds are termed music while unpleasant sounds are classified as noise. Characteristics of a sound are those properties which determine its quality as pleasant or unpleasant. Two of these properties, pitch and loudness, are very important. These properties depend on the mathematical quantities described in the previous section. The pitch of a sound determines how shrill (sharp) or grave (heavy) it is. Pitch of a sound cannot be directly calculated so we determine it from the sound’s frequency. High frequency sounds are called high-pitched while low frequency sounds are low-pitched. To control the pitch of a sound wave we control the frequency of the vibrating source. The loudness of a sound determines its level. It depends on the amplitude of the sound wave. The larger the amplitude of the sound wave, the louder the sound is. Sounds with small amplitude are characterized as faint sounds. Loudness is increased by increasing the area of the vibrating surface. Propagation of sound waves depends on the presence of a medium. They cannot propagate in vacuum. The frequency of a sound wave depends on the frequency of vibration of the source. The faster the movement, the higher the frequency and the pitch. The loudness of a sound depends on the area of the vibrating surface. The larger the area, the louder the sound. Solution to Closed book Mystery: Top most is high-pitched. Lower-most is fainter. Classroom Activity (Page 134): To explain the relation between amount of matter and kind of sound, follow the activity on page 134 of the book. Tap all the bottles one by one with the spoon when they are empty. All of them produce the same sound. Now fill them with increasing amounts of water. Place them in a line in increasing order of water’s mass from left to right. Now tap them one by one again. All of them will produce different sounds. Now try to give order to your tapings. This will produce musical compositions. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is pitch? How is it related to frequency? 2. What is loudness? How is it related to amplitude? 3. What is the difference between shrill and grave sounds? 4. What is the difference between loud and faint sounds? Lesson 4 Topic: (10.4: Applications of Sound) Teaching objectives: ⦁ Recall sound and sound waves. ⦁ Introduce applications of sound. ⦁ Relate wave terms to applications of sound. Key vocabulary: Pitch, loudness, surface area, medium, movement, source, observer, doorbell, siren, telephone, radio, stereo, smoke detector, security alarm. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this unit is to introduce the applications of sound waves. It will help the students to understand that sound is not only a natural phenomenon but also it can be applied in many devices. At this level, students have prior knowledge of these applications. Now, they will be introduced to them in detail. Introduction: Ask the students, “What happens when they press the button of a doorbell or call someone over the phone? How is sound related to these processes?” Write the responses on writing board. Tell the students that today we will be learning about the application of sound in different devices. 147 Teacher Resource Pack Guide Science 7 (The teacher will announce that today we are going to begin topic 10.4 from the 10th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation: Now, teacher will explain to the students that in this section we will study some devices which produce different sounds. These devices are energy converters which convert other forms of energy into specific sounds that are required. In a simple doorbell, electrical energy is provided to the circuit of the bell when we press the button. This is converted into kinetic energy of the hammer which strikes the gong and produces sound. It produces a ringing sound. In a musical doorbell, advanced circuitry is used which includes components called transistors and resistors. The circuit of a siren in a police car or an ambulance also contains combinations of transistors and resistors. The source of energy is the battery of the vehicle which has stored chemical energy. This energy is converted into electrical energy which is converted into a hooting sound by the siren. Old telephones contained a small bell which rang due to a small amount of current that flowed through it when someone called. Nowadays cellular phones are used, which can produce any sound during an incoming call. The conversion of energy in both cases is from electrical energy to sound. However the sources of energy are different. In old telephones it was the electrical energy from small generators at the customer exchange stations. In cellular phones the generator is replaced by a small rechargeable battery. The voice of the caller that we hear through the earpiece is also heard after two energy conversions. First, the speaker speaks in the mouthpiece. His sound is converted into electrical signals of low energy. These electrical signals move through the cables and are received at the listener’s end. There the electrical signals are again converted into sound by a decoder. A radio also uses energy transfer through radio waves, but unlike a cellular phone, it is a one-way communication system. Transmission from a broadcast station is taken to the radio set by radio waves. The receiving circuit of a radio set is provided electrical energy through batteries or from the power supply of the house. The radio signals are then decoded into sound which is the music or the news that we enjoy. Sound systems have stereophonic (or simply stereo) speakers or headphones that give the feeling of sound coming from different directions. This is achieved by using two channels (pathways of sound waves) of sound instead of one as in monophonic (mono) sound systems. The energy conversion is still the same that is, from electrical to sound. A smoke detector is an electric circuit set up in such a way that when the smoke enters the detector the current due to ionized gas inside is disrupted and the current stops. The inverter (a component which turns the bell on when current stops) in the circuit turns the bell on when the current stops. Motion sensing security alarms contain infrared detectors. As soon as the infrared radiation of an intruder is received by the detector, the circuit is turned on. The electrical energy of the circuit is used to ring the bell. Conclusion: In last 5-10 minutes, recall the lesson by asking questions from students like. 1. How does a doorbell work? How is sound produced in a siren? 2. Describe a telephone’s working. 3. Describe application of sound in radio and stereo. 4. What is the purpose of smoke detectors and security alarms? Review Exercise A. 1. 2. 3. Choose the correct answer and fill the circle: A sound wave moves the particles: up and down back and forth in circles with itself Which of the following statements is correct about the pitch of the sound? it depends on wavelength decreasing the amplitude increases the pitch increase in the frequency decreases the pitch increase in the frequency increases the pitch Which of the following statements is Not correct about the loudness of a sound? 148 Teacher Resource Pack Guide it depends on frequency Science 7 it depends on amplitude decreasing the area of the vibrating object decreases loudness increasing the area of the vibrating object increases loudness 4. A sound of frequency 44,000 hertz can be heard by: a cat a dog both cat and dog humans 5. Electrical energy to a doorbell is supplied by: gong hammer electrical power of a house none of these 6. Which of the following statements is correct for the siren of a police car? petrol produces sound the car's battery converts chemical energy into sound movement of the car produces sound of the siren the car's battery converts chemical energy into electrical energy 7. Cellular phone communication is done through: electric signals winds radio waves power cables 8. A monophonic sound system uses: two channels of sound three channels of sound one channel of sound four channels of sound 9. Smoke alerts us by: seeing smoke hearing bell sound flow of current switching off light 10. Motion sensing security alarms detect: sound waves longitudinal waves radio waves infrared radiation B. Answer the following questions shortly. 1. Differentiate between transverse and longitudinal waves. Ans: Transverse waves are those in which a wave moves forward but the particles vibrate up and down. A longitudinal wave moves forward and the particles of the medium also vibrate back and forth. 2. How does the frequency of a sound wave determine its pitch? Ans: High frequency sounds are called high-pitched while low frequency sounds are low-pitched. 3. How does the loudness of a wave depend on amplitude? Ans: The loudness of a sound determines its level. It depends on the amplitude of the sound wave. The larger the amplitude of the sound wave, the louder the sound is. 4. What does the area of the vibrating object tell us about the sound it produces? Ans: The loudness of a sound depends on the area of the vibrating surface. The larger the area, the louder the sound. 5. What does the movement of the vibrating object tell us about the sound it produces? Ans: The frequency of a sound wave depends on the frequency of vibration of the source. The faster the movement, the higher the frequency and the pitch. 6. What is the audible frequency range for humans? Ans: Audible frequency range of lies between 20 hertz to 20,000 hertz. 7. How does a stereo work? Ans: Sound systems have stereophonic (or simply stereo) speakers or headphones that give the feeling of sound coming from different directions. This is achieved by using two channels (pathways of sound waves) of sound instead of one as in monophonic (mono) sound systems. The energy conversion is still the same that is, from electrical to sound. 8. How does smoke alarm alert us of fire? 149 Teacher Resource Pack Guide Science 7 Ans: A smoke detector is an electric circuit set up in such a way that when the smoke enters the detector the current due to ionized gas inside is disrupted and the current stops. The inverter (a component which turns the bell on when current stops) in the circuit turns the bell on when the current stops. 9. Describe the process of radio transmission. Ans: Transmission from a broadcast station is taken to the radio set by radio waves. The receiving circuit of a radio set is provided electrical energy through batteries or from the power supply of the house. The radio signals are then decoded into sound. 10. What causes ringing in telephone sets? Ans: The conversion of energy is from electrical energy to sound. In old telephones it was the electrical energy from small generators at the customer exchange stations. In cellular phones the generator is replaced by a small rechargeable battery. C. Answer the following questions in details. 1. Write a detailed note on wave terms. Ans: Wave Terms: A wave is a disturbance which carries energy. To gain knowledge of the properties and behaviour of waves, we have worked out some terms. These terms are mathematical quantities which can be calculated. The following important wave terms will give you an insight about waves. Wavelength: We have stated that a wave travels from one place to another Transverse waves are produced by up and down vibration while sound travels as longitudinal waves (back and forth vibration). During the movement of a transverse wave some particles of the medium move up to produce peaks called crests. Other particles move down to produce valleys called troughs. The distance between two successive crests (or troughs) is called wavelength of a transverse wave. Sound energy from a vibrating object moves the particles of the medium back and forth and a longitudinal wave is set up. Along the waves regions are produced where particles move towards each other. These regions are called compressions. The regions where particles move away from each other are called rarefactions. One compression is separated from the other by a rarefaction. This distance between two compressions (or rarefactions) is called wavelength. “The distance between the midpoints of two successive compressions (or rarefactions) is called the wavelength of a sound wave.” Time Period and Frequency: Sound is produced by a vibrating object. Time taken by a vibrating object to complete one back and forth vibration is called time period (T). The vibrating object and the particles of the medium vibrate with the same time period. Time period is usually calculated in seconds (s). During one time period, the wave covers a distance of one wavelength. Frequency (f) of a sound wave is the number of vibrations made by the particles of the medium in one second. Frequency is calculated in hertz (Hz). Frequency and time period are related by the formula, 1 𝑓= 𝑇 Amplitude: The amplitude of a transverse wave refers to the vertical distance between the mean position and a crest (or trough). In case of a sound wave (which is longitudinal) the amplitude is calculated by the variation of pressure of the medium due to compressions (high pressure regions) and rarefactions (low pressure regions). Hence, the amplitude of a sound wave can be defined as, “The maximum pressure change in the medium is the amplitude of a sound wave.” Amplitude is denoted by “A.” 2. Explain how frequency and amplitude determine pleasantness or unpleasantness of a sound. Ans: The pleasantness and unpleasantness are determined by frequency and amplitude because these quantities determine the pitch and loudness of a sound. 150 Teacher Resource Pack Guide Science 7 The pitch of a sound determines how shrill (sharp) or grave (heavy) it is. Pitch of a sound cannot be directly calculated so we determine it from the sound’s frequency. High frequency sounds are called highpitched while low frequency sounds are low-pitched. Sounds with balanced pitch appear pleasant. To control the pitch of a sound wave we control the frequency of the vibrating source. The loudness of a sound determines its level. It depends on the amplitude of the sound wave. The larger the amplitude of the sound wave, the louder the sound is. Sounds with small amplitude are characterized as faint sounds. Sounds with balanced loudness are pleasant. Loudness is increased by increasing the area of the vibrating surface. 3. “Different applications of sound make life easier.” Explain. Ans: Applications of Sound: Sound is used in many devices which produce different sounds. These devices are energy converters which convert other forms of energy into specific sounds that are required. Doorbell: In a simple doorbell, electrical energy is provided to the circuit of the bell when we press the button. This is converted into kinetic energy of the hammer which strikes the gong and produces sound. It produces a ringing sound. In a musical doorbell, advanced circuitry is used which includes components called transistors and resistors. Siren: The circuit of a siren in a police car or an ambulance also contains combinations of transistors and resistors. The source of energy is the battery of the vehicle which has stored chemical energy. This energy is converted into electrical energy which is converted into a hooting sound by the siren. Telephone: Old telephones contained a small bell which rang due to a small amount of current that flowed through it when someone called. Nowadays cellular phones are used, which can produce any sound during an incoming call. The conversion of energy in both cases is from electrical energy to sound. However the sources of energy are different. In old telephones it was the electrical energy from small generators at the customer exchange stations. In cellular phones the generator is replaced by a small rechargeable battery. The voice of the caller that we hear through the earpiece is also heard after two energy conversions. First, the speaker speaks in the mouthpiece. His sound is converted into electrical signals of low energy. These electrical signals move through the cables and are received at the listener’s end. There the electrical signals are again converted into sound by a decoder. Radio: A radio also uses energy transfer through radio waves, but unlike a cellular phone, it is a one-way communication system. Transmission from a broadcast station is taken to the radio set by radio waves. The receiving circuit of a radio set is provided electrical energy through batteries or from the power supply of the house. The radio signals are then decoded into sound which is the music or the news that we enjoy. Stereo: Sound systems have stereophonic (or simply stereo) speakers or headphones that give the feeling of sound coming from different directions. This is achieved by using two channels (pathways of sound waves) of sound instead of one as in monophonic (mono) sound systems. The energy conversion is still the same that is, from electrical to sound. Smoke Detector: A smoke detector is an electric circuit set up in such a way that when the smoke enters the detector the current due to ionized gas inside is disrupted and the current stops. The inverter (a component which turns the bell on when current stops) in the circuit turns the bell on when the current stops. Security Alarm: Motion sensing security alarms contain infrared detectors. As soon as the 151 Teacher Resource Pack Guide Science 7 infrared radiation of an intruder is received by the detector, the circuit is turned on. The electrical energy of the circuit is used to ring the bell. 4. Explain the working principle of: a. Smoke Detector b. Security Alarm c. Radio Ans: The working principles of smoke detector, security alarm and radio are as follows: a. Smoke Detector: A smoke detector is an electric circuit set up in such a way that when the smoke enters the detector the current due to ionized gas inside is disrupted and the current stops. The inverter (a component which turns the bell on when current stops) in the circuit turns the bell on when the current stops. b. Security Alarm: Motion sensing security alarms contain infrared detectors. As soon as the infrared radiation of an intruder is received by the detector, the circuit is turned on. The electrical energy of the circuit is used to ring the bell. c. Radio: A radio also uses energy transfer through radio waves, but unlike a cellular phone, it is a one-way communication system. Transmission from a broadcast station is taken to the radio set by radio waves. The receiving circuit of a radio set is provided electrical energy through batteries or from the power supply of the house. The radio signals are then decoded into sound which is the music or the news that we enjoy. D. Solve the following numerical problems using calculator. 1. The frequency of a sound wave is 50 hertz. Calculate the time period in seconds. Given that: Frequency = f = 50 Hz To be found: Time period = T = ? Formula to be used: 1 𝑓= 𝑇 Calculations: 1 𝑇= 𝑓 1 𝑇= 50 𝑇 = 0.02 𝑠 2. The time period of a wave is 2s. Calculate the frequency in hertz. Given that: Time Period = T = 2 s To be found: Frequency = f = ? Formula to be used: 1 𝑓= 𝑇 Calculations: 1 𝑓= 2 𝑓 = 0.5 𝐻𝑧 Numerical with thought experiment. 152 Teacher Resource Pack Guide Science 7 1. A man, a dog and an elephant are standing in a row. Two sound waves of the same period T = 4.8 × 10-3 s travel towards them. Which of the creatures will respond to the waves? Also, explain your answer. 1 𝑓= 𝑇 1 𝑓= 4.8 𝑋 10−3 𝑓 = 208.3 𝐻𝑧 All of them will respond because this frequency lies in the audible frequency range of all of them. 2. One of the waves, which is wave A, has a higher pressure difference between its compressions and rarefactions than the other that is wave B. Which sound will be louder, A or B? Explain your answer with a reference to the amplitude of a sound wave. Ans: Wave A will be louder because its pressure difference is higher. A louder wave has larger amplitude. For sound waves amplitude is equal to the pressure difference which higher in wave A. Model Paper No. 1 Section – A: Multiple Choice Questions Marks: 40 Time: 50 Minutes Roll No. __________ Choose the correct option. 40 1. Percentage of Earth surface which is covered by fresh water is: 25% 2.5% 97% 20% 2. The form of water with high concentration of salt is: rain water fresh water ocean water ground water 3. The purpose of adding chlorine is to make water: less turbid germ free pleasant tasteless 4. Rivers and lakes are sources of: ocean water fresh water groundwater salt water 5. The place where fresh water and salt water meet is called: estuary delta aquifer none of these 6. We can make the water salt-free by using the process of: water treatment filtration distillation chlorination 7. The building block of matter is atom. The reason for this concept was that atom considered as: smallest particle divisible particle indivisible particle only available particle 8. the shell that can accommodate only 2 electrons is: K L M N 9. Combining power of chlorine is: 2 1 4 3 10. Radioactive isotopes are unstable because: they are weak their valence shell is incomplete they have heavy nucleus they have high energy 11. The sub-atomic particles found in the nucleus are: electron, proton electron, neutron proton, neutron only protons 12. The letter “Z” in chemistry represents: atomic number mass number valency valence electronic shell 153 Teacher Resource Pack Guide 13. Science 7 The arrangement of electrons in sodium (Na-11). 2, 8, 1 2, 8, 2 2, 1, 8 1, 2, 8 14. Crushing of can is a: physical change chemical change irreversible change radioactive change 15. Burning of wood is: physical change chemical change reversible change none of these 16. During the candle burning, wax: vaporizes condense boil decompose 17. Another name of vinegar is: silver chloride acetic acid sodium chloride Sodium bicarbonate 18. Methane + oxygen ________ + ________ + ________ carbon dioxide + oxygen + heat carbon dioxide + water + energy oxygen + water + energy water + heat + energy 19. Hydropower generation is a ________ change. physical chemical all of these irreversible 20. Polyethylene is made by _______. ethylene units styrene units propylene units none 21. To reverse the flow of heat one must: put the hot body close to the cold body keep both bodies hot keep both bodies cold provide energy to the cold body 22. Which of the following options correctly relates the mode of transfer of heat with the natural process? conduction, green house effect convection, solar energy through vacuum radiation, winds convection, ocean currents 23. Which of the following processes result from convection? gliding of birds gliding of pilots both of these expansion of concrete 24. A metal pot of water is being heated on a stove. Which of the following process is NOT happening? conduction convection radiation evaporation 25. Which of the following is most suitable for making ladles? wool copper wood iron 26. A vacuum flask prevents: conduction convection radiation all of these 27. During a convection current, which of the following does not happen? hot air sinks hot air rises cold air sinks particles move 28. Which of the following combinations represents primary colours? red, yellow, blue red, purple, blue red, green, blue red, orange, green 29. Rainbow in the sky is caused by: prism winds lightning water droplets 30. An opaque object is coloured because of: absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one 31. The principle of a reflecting prism is: reflection dispersion refraction total internal reflection 32. A prism based periscope is better because: it produces a clear, magnified image prisms do not rust like aluminum coated mirrors both of these prisms disperse light 33. Total internal reflection occurs: 154 Teacher Resource Pack Guide Science 7 at critical angle after critical angle at the normal in the rare medium 34. Motion sensing security alarms detect: sound waves longitudinal waves radio waves infrared radiation 35. A sound wave moves the particles: up and down back and forth in circles with itself 36. Which of the following statements is correct about the pitch of the sound? it depends on wavelength decreasing the amplitude increases the pitch increasing the frequency decreases the pitch increasing the frequency increases the pitch 37. Which of the following statements is not correct about the loudness of a sound? it depends on frequency loudness depends on amplitude decreasing the area of the vibrating object decreases loudness increasing the area of the vibrating object increases loudness 38. Which component of a smoke detector turns on the bell when the current due to ionized gas is disrupted? converter inverter gong hammer 39. A denser medium refracts light because: light changes colour in the denser medium light stops in the denser medium light changes speed in the denser medium light is converted into sound 40. After the transfer of heat from the hot body to cold body, the cold body: gets warmer than the hot body becomes equal in temperature to the hot body gets colder than the hot body does not absorb heat at all Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) How does water make food for plants? (2) (b) Write uses of water in houses. (2) (c) Differentiate between “green water” and “blue water”? (2) Q.2: (a) Which type of impurities remains suspended in water? (3) (b) What are the effects of impurities on water quality? (3) Q.3: (a) Write masses of electron, proton and neutron. (2) (b) Fill the electrons in 16S, also draw the diagram. (2) (c) Write uses of isotopes in agriculture. (2) Q.4: () MgCl2 is a chemical formula of an ionic compound. (a) Write the name of this compound. (1) (b) Guess the valency of each atom in this compound. (1) (c) Mention the ions formed in this compound. (2) (d) Make the ionic structure of its ions showing the electronic distribution in its orbits. (2) Q.5: Explain with examples that physical and chemical changes may occur simultaneously.(3) (b) Describe harmful effects of using hydrocarbons as fuel. (3) Q.6: (a) How does a solid conduct heat? (2) (b) Write a detailed note on the differences between conduction, convection and radiation.(4) Q.7: (a) What causes a convection-current? (2) (b) What causes refraction? (2) (c) Why do submarines have prism based periscopes? (2) Q.8: (a) How does a swimming pool appear less deep? (2) (b) Differentiate between the working of conductors and insulators. (4) 155 Teacher Resource Pack Guide Science 7 Q.9: (a) Why do submarines have prism based periscopes? (2) (b) Write a detailed note on refraction, its cause and its occurrence in the environment. (4) Q.10: (a) How does the loudness of a wave depend on amplitude? (2) (b) Explain how frequency and amplitude determine pleasantness or unpleasantness of a sound. (4) Model Paper No. 2 Section – A: Multiple Choice Questions Marks: 40 Time: 50 Minutes Roll No. __________ Choose the correct option. 40 1. Neutrons are discovered by: J.J. Thomson Rutherford James Chadwick Mosley 2. The mass of electron is: 1.67 × 10-27 kg 9.11 × 10-31 kg 1.67 × 10-27 g 9.11 × 10-31 g 3. Atomic number is equal to Number of: protons neutrons electrons quarks 4. The arrangement of electrons in different shells is known as: stability valence electrons electronic configuration shells 5. The number of missing electrons in L-shell of oxygen are: 1 2 3 4 6. Group number represents: valency charge anion cation 7. In an anion, number of electrons is: more than no of proton less than no of proton equal to than of proton none 8. Chemical composition of ice and water vapour is: different same not known equal 9. Browning of apple is due to reaction with: carbon dioxide oxygen sulfur nitrogen 10. When an egg decays, it produces the smell of: carbon sulphur oxygen nitrogen 11. Fossil fuels are: renewable non-renewable conservation non-conservative 12. Fertilizer is any substance added to the soil to make it more: barren fertile dry wet 13. The property of absorbing moisture from air is called: condensation evaporation sublimation hygroscopicity 14. To make plastic Naphtha is subjected: cracking moulding bending forwarding 15. () is the sign of ________ reactions. reversible reactions irreversible reactions chemical reactions physical reactions 16. The polymer in your hair and nails is: polyethylene polystyrene keratin carbohydrates 17. Bakelite is a: 156 Teacher Resource Pack Guide Science 7 fertilizer synthetic plastic oil ghee 18. Baking a bread is a: physical process chemical process reversible process polymerization process 19. Combustion is a ________ process. endothermic process exothermic process physical process reversible process 20. Formula of Ammonium phosphate is ________. NH4NO3 [(NH4)2 SO4] K2SO4 [(NH4)3 PO4] 21. Which of the following options correctly relates the mode of transfer of heat with the natural process? conduction, greenhouse effect convection, solar energy through vacuum radiation, winds convection, ocean currents 22. Which of the following processes result from convection? gliding of birds gliding of pilots both of these expansion of concrete 23. To reverse the flow of heat one must: put the hot body close to the cold body keep both bodies hot keep both bodies cold provide energy to the cold body 24. A metal pot of water is being heated on a stove. Which of the following process is NOT happening? conduction convection radiation evaporation 25. Which of the following is most suitable for making ladles? wool copper wood iron 26. Which of the following combinations represents primary colours? red, yellow, blue red, purple, blue red, green, blue red, orange, green 27. A vacuum flask prevents: conduction convection radiation all of these 28. During a convection current, which of the following does not happen? hot air sinks hot air rises cold air sinks particles move 29. Rainbow in the sky is caused by prism winds lightning water droplets 30. An opaque object is coloured because of: absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one 31. The principle of a reflecting prism is: reflection dispersion refraction total internal reflection 32. A prism based periscope is better because: it produces a clear, magnified image prisms do not rust like aluminum coated mirrors both of these prisms disperse light 33. Total internal reflection occurs: at critical angle after critical angle at the normal in the rare medium 34. Motion sensing security alarms detect: sound waves longitudinal waves radio waves infrared radiation 35. A sound wave moves the particles: up and down back and forth in circles with itself 36. Total internal reflection occurs: 157 Teacher Resource Pack Guide Science 7 at critical angle after critical angle at the normal in the rare medium 37. Which component of a smoke detector turns on the bell when the current due to ionized gas is disrupted? converter inverter gong hammer 38. After the transfer of heat from the hot body to cold body, the cold body: gets warmer than the hot body becomes equal in temperature to the hot body gets colder than the hot body does not absorb heat at all 39. A denser medium refracts light because: light changes colour in the denser medium light stops in the denser medium light changes speed in the denser medium light is converted into sound 40. Which of the following statements is not correct about the loudness of a sound? it depends on frequency loudness depends on amplitude decreasing the area of the vibrating object decreases loudness increasing the area of the vibrating object increases loudness Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) How does water balance our ecosystem? (3) (b) Differentiate between purified water and distilled water. (2) (c) What is meant by Aquifer? (1) Q.2: (a) Draw flow sheet diagram of water treatment process. (4) (b) Write pre-treatment step of water processing. (2) Q.3: (a) What is nucleus of an atom? Who discovered it? (2) (b) What will be the number of protons in an element X that have that has 30 neutrons and its mass number in 56. (2) (c) Write and draw isotopes of hydrogen. (2) Q.4: (a) Write the difference between physical and chemical changes with examples. (3) (b) Write threats of polythene bags to our environment. (3) Q.5: Write physical and chemical properties of fertilizers. (3) (b) Complete the given table by keeping in mind the effort of heat.. (3) Q.6: (a) What does the refractive index tell us? (2) (b) Write a detailed note on refraction, its cause and its occurrence in the environment.(4) Q.7: (a) How does a stereo work? (2) (b) What does the refractive index tell us? (2) (c) Describe the process of radio transmission? (2) Q.8: (a) When does a prism disperse light? (2) (b) Write a note on refractive index and explain its mathematical formula. (4) Q.9: (a) What causes ringing in telephone sets? (2) (b) Explain how frequency and amplitude determine pleasantness or unpleasantness of a sound. (4) Q.10: (a) Describe the process of radio transmission. (2) (b) Write a note on the uses of colour and coloured lights. (4) Model Paper No. 3 Section – A: Multiple Choice Questions Marks: 40 158 Time: 50 Minutes Teacher Resource Pack Guide Science 7 Roll No. __________ Choose the correct option. 40 1. Water that is panacea according to Muslim belief: Ganga Zam Zam lake sea 2. Human brain contain ________ water: 82% 75% 70% 22% 3. The biggest lake on earth is: lake Hunza lake Baikal lake Saif-ul-maluk none 4. Washing becomes due to difficult. hard water soft water fresh water ground water 5. Alum is: aluminium sulphate sodium sulphate aluminium carbonate aluminium phosphate 6. The settled flocs are called: alum debris sludge sediment 7. Amount of water to produce one kg of steel is: 1.665 liter 766 liter 255 liter 125 liter 8. Neutrons have charge: positive negative no all 9. Atomic numbers were discovered by. Henry Moseley Chadwick Rutherford J.J. Thomson 10. The electronic distribution of Neon is: 2, 2 2, 4 2, 6 2, 8 11. An element has 79 protons, 79 electrons and 118 neutrons. Its mass number is: 158 197 355 39 12. The M-shell of chlorine has electrons: 5 6 7 8 13. Write valency of phosphorus: P P2 P3 P414. How many neutrons tritium has? 1 2 3 4 15. Change of solid state into vapours is called: evaporation condensation melting freezing 16. Formula of ethylene is: C2H6 C2H4 C2H2 C2H 17. A catalyst in hydrogenation is: Cu Cr Ni Ag 18. Copper sulphate (blue) Copper sulphate (white). It is an example of: reversible reaction irreversible reaction unique reaction polymerization reaction 19. Bleach decolorizes the food color it is: physical change chemical change reversible change temporary change 20. Solar energy is: yellow energy green energy blue energy black energy 21. Which of the following processes result from convection? 159 Teacher Resource Pack Guide 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. Science 7 gliding of birds gliding of pilots both of these expansion of concrete During a convection current, which of the following does not happen? hot air sinks hot air rises cold air sinks particles move Which of the following options correctly relates the mode of transfer of heat with the natural process? conduction, greenhouse effect convection, solar energy through vacuum radiation, winds convection, ocean currents A metal pot of water is being heated on a stove. Which of the following process is NOT happening? conduction convection radiation evaporation Which of the following is most suitable for making ladles? wool copper wood iron To reverse the flow of heat one must: put the hot body close to the cold body keep both bodies hot keep both bodies cold provide energy to the cold body Rainbow in the sky is caused by: prism winds lightning water droplets A vacuum flask prevents conduction convection radiation all of these Which of the following combinations represents primary colours? red, yellow, blue red, purple, blue red, green, blue red, orange, green An opaque object is coloured because of: absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one The principle of a reflecting prism is: reflection dispersion refraction total internal reflection A prism based periscope is better because: it produces a clear, magnified image prisms do not rust like aluminum coated mirrors both of these prisms disperse light Total internal reflection occurs: at critical angle after critical angle at the normal in the rare medium A sound wave moves the particles: up and down back and forth in circles with itself Which of the following statements is correct about the pitch of the sound? it depends on wavelength decreasing the amplitude increases the pitch increasing the frequency decreases the pitch increasing the frequency increases the pitch Motion sensing security alarms detect: sound waves longitudinal waves radio waves infrared radiation After the transfer of heat from the hot body to cold body, the cold body: gets warmer than the hot body becomes equal in temperature to the hot body gets colder than the hot body does not absorb heat at all Which of the following statements is not correct about the loudness of a sound? it depends on frequency loudness depends on amplitude decreasing the area of the vibrating object decreases loudness 160 Teacher Resource Pack Guide Science 7 increasing the area of the vibrating object increases loudness 39. Which component of a smoke detector turns on the bell when the current due to ionized gas is disrupted? converter inverter gong hammer 40. Which of the following statements is not correct about the loudness of a sound? light changes colour in the denser medium light stops in the denser medium light changes speed in the denser medium light is converted into sound Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) Briefly describe ground water resources. (3) (b) Write water treatment process to make it mineral free. (3) Q.2: (a) An element has 13 electrons and 14 neutrons. Write it atomic number and mass number. (2) (b) Define octet rule. (1) (c) Define radioactive isotopes. Write their two uses. (3) Q.3: (a) Differentiate between homo-atomic and hetero-atomic molecules with examples. (3) (b) Write number of protons and neutrons in C-12, C-13 and C-14 and draw their structures. (3) Q.4: (a) Identify physical or chemical changes. Also give reason for identification. (6) (a) Solubility (b) Filtration (c) Distillation (d) Combustion (e) Evaporation (d) Polymerization Q.5: Give 2 examples of synthetic fertilizer and 2 examples of natural fertilizers. (2) (b) Define Hydropower generation. (1) (c) How to identify a physical change? (2) Q.6: (a) What purpose does the trapped air in a vacuum flask serve? (2) (b) Explain the flow of heat between two bodies by drawing a diagram. (4) Q.7: (a) Why do submarines have prism based periscopes? (2) (b) What causes refraction? (2) (c) What causes a convection-current? (2) Q.8: (a) How is conduction applied in an electric iron? (2) (b) Differentiate between the working of conductors and insulators. (4) Q.9: (a) How does a swimming pool appear less deep? (2) (b) Explain with examples how refraction has made our lives easier. (4) Q.10: (a) What happens when the incident ray strike exactly at critical angle? (2) (b) Write a detailed note on refraction, its cause and its occurrence in the environment. (4) ‘Detailed Division of Syllabus’ 3rd term Week 1 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 2 161 Unit– 11 T – 11.1: T – 11.2: T – 11.2.1: T – 11.2.3: T – 11.3: T – 11.4: Circuits and electric current Electric current Electric Circuits Voltage and Resistance Energy Transfer in a Circuit Measuring voltage and current Test Exercise – 1 Effects of Electric Current Teacher Resource Pack Guide Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Week 3 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 162 Science 7 T – 11.5: T – 11.6: T – 11.7: T – 11.8: Uses of Electricity Hazards of Electricity Safety Devices for Circuits Household circuits and billing of electricity Review exercise Review exercise Revision of Unit - 11 Revision of Unit – 11 Unit – 12: Investigation the space T – 12.1: Beyond the Solar System T – 12.2: The big bang and the origin of the universe T – 12.3: Celestial Bodies T – 12.4: Looking at Stars Review Exercise Week 4 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Review Exercise Revision of Unit – 12 Revision of Unit – 12 Revision of Unit – 1 Revision of Unit – 1 Revision of Unit –2 Week 5 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Revision of Unit –2 Revision of Unit –3 Revision of Unit –3 Revision of Unit –4 Revision of Unit –4 Revision of Unit –5 Week 6 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Revision of Unit –5 Revision of Unit –6 Revision of Unit –6 Revision of Unit –7 Revision of Unit –7 Revision of Unit –8 Week 7 Day 1 Day 2 Day 3 Revision of Unit –8 Revision of Unit –9 Revision of Unit –9 Teacher Resource Pack Guide Science 7 Day 4 Day 5 Day 6 Revision of Unit –10 Revision of Unit –10 Revision of Unit –11 Week 8 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Revision of Unit –11 Revision of Unit –12 Revision of Unit –12 Writing Test of 1st Term Writing Test of 2nd Term Writing Test of 3rd Term 3rd Term Unit # 11 CIRCUITS AND ELECTRIC CURRENT Lesson 1 Topic: (11.1: Electric Current) Teaching objectives: ⦁ Recall the difference between conventional and electronic current. Key vocabulary: Current, charge, electron, conventional, electronic. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this unit is to introduce electric current and electric circuit. It will help the students to understand that electric current flows to make the working of electric appliances possible. At this level, students have no prior knowledge of flow of electric current and its direction. Now, they will be introduced to these concepts in detail. Introduction Ask the students: How do bulb, fan and electric heater work? Write the responses on writing board. Tell the students that today we will be learning the reason behind the working of these appliances that is, current. (The teacher will announce that today we are going to begin 11th chapter from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that in previous classes, we studied that electric charges are of two types: positive and negative. Like charges repel and unlike charges attract each other. Static electricity describes the properties and behaviour of charges when they are rest. In this chapter we will step ahead and discuss moving electric charges. Let us start by studying electric current. An electric circuit is a closed loop of electric wires connected with components such as a battery and load (say a light-bulb or a small motor). The battery provides the electrical energy which is converted into light or motion. Electrical energy is carried by electric charges that flow through the wires. This movement of charges is called current. “The flow of electric charges around the circuit is called electric current.” Current is symbolized by “I” and is measured in amperes (A). It is different from electrical energy. Electrical energy is the ability of an electrical source (battery or cell) to do work while current is the flow of charges that carry electrical energy. We take the direction of flow of current from the positive terminal to the negative terminal of the battery. Current flowing in this direction is called conventional current. 163 Teacher Resource Pack Guide Science 7 Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 5. Define electric current. 6. Differentiate between electronic and conventional current. Lesson 2 Topic: (11.2: Electric Circuits) (11.2.1: Voltage and Resistance) Teaching objectives: ⦁ Introduce electric circuit. ⦁ Introduce components of an electric circuit. Key vocabulary: Circuit, source, battery, load, conductor, open, closed, switch, lamp, ammeter, voltmeter, resistor. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce electric circuits, voltage and resistance. It will help the students to understand that electric circuit is necessary for the flow of electric current. At this level, students have no prior knowledge of flow of electric circuits. Now, they will be introduced to them in detail. Introduction Ask the students: What makes current flow? Write the responses on writing board. Tell the students that today we will be learning the reason behind the flow of current and its necessary conditions. (The teacher will announce that today we are going to begin topic 11.2 from the 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that an electric circuit is a complete or closed path through which charge can flow from the positive terminal to the negative terminal of a source of electrical energy (a battery or a cell). It usually consists of four main components: 7. A source of electrical energy that drives the charges (battery or cell) 8. A load on which the charges do some useful job (bulb, motor etc.) 9. Electrical conductors to connect the components (copper wires) 10. Switch to open or close the circuit The battery drives the electrical charges. To move the charges a battery does work on them. Work done by the battery on a single charge to move it once through the circuit is called voltage. Its symbol is V and is measured in volts (V). Electric current is the flow of charges in a circuit. Does this flow take place without any difficulty? The answer is no. As the charge particles move through a wire of an electrical circuit, they collide with the atoms of the wire’s material. This produces an opposition to the flow of current which is called resistance. It produces heat. “The opposition offered to the flow of current is called resistance.” It is symbolized as ‘R’ and is measured in ohms (Ω). Besides the resistance offered by the wires, we can also limit the flow of current according to our own requirement. This is achieved by using circuit components called resistors. Voltage of a battery and resistance of a conductor through which electric charges flow is given by the following mathematical formula. 𝑉 = 𝐼𝑅 164 Teacher Resource Pack Guide Science 7 Here V, I and R represent the voltage, the current and the resistance respectively. Usually the resistance remains fixed. In that case, increasing the voltage increases the current. To explain the voltage and current formula, follow the worked example 1.1 on page 142. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 1. What is an electric circuit? 2. What are the basic components of an electric circuit? 3. Define voltage and resistance. What is resistance? Lesson 3 Topic: (11.2.2: Series and Parallel Circuits) (11.2.3: Energy Transfer in a Circuit) Teaching objectives: ⦁ Introduce series and parallel circuits. ⦁ Identify the disadvantage a series circuit. ⦁ Identify the process of energy transfer in a circuit. Key vocabulary: Circuit, series, parallel, components, energy transfer. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce types of electric circuits that are used for different purposes, namely: series and parallel. It will help the students to understand the difference between series and parallel circuits. At this level, students have no prior knowledge of flow of types of electric circuits. Now, they will be introduced to them in detail. Introduction Ask the students: Why do electric fan and light bulb have different switches on the board in our houses? Write the responses on writing board. Tell the students that today we will be learning the types of electric circuits used for different purposes. (The teacher will announce that today we are going to begin topic 11.2.2 from the 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that electrical circuits are classified into two main types according to the arrangement of the components that make the load (resistors, bulbs, motor etc.) These types are series circuit and parallel circuit. In a series circuit, all the components are connected end to end (in a line). That is, they make a single loop or path of current to form the circuit. On the other hand, in a parallel circuit resistors or bulbs are connected in branches that are parallel to each other. Multiple loops or paths of current are formed in a parallel circuit. Current is divided among the appliances but energy supplied to each appliance remains the same. The same current flows through all the components of a series circuit due to single path of flow. This means that if one of the components is destroyed due to some reason, current through the whole circuit stops. The purpose of an electric circuit is to convert electrical energy into other forms of energy. This conversion of energy is accomplished through energy transfer from the battery to the load. Stored chemical energy of a battery or a cell is used by it to do work on electrical charges. This work drives them through the circuit and hence they reach the load where, the charges do work on the load and the energy is finally converted into light, heat or kinetic energy. 165 Teacher Resource Pack Guide Science 7 Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 4. What is an electric circuit? 5. What are the types of electric circuit? 6. What is the disadvantage of a series circuit? Lesson 4 Topic: Teaching objectives: (11.3: Measuring voltage and current) ⦁ Recall voltage and current. ⦁ Recall ampere and volt. ⦁ Introduce voltmeter. ⦁ Introduce ammeter. Key vocabulary: Voltage, current, ampere, volt, voltmeter, ammeter. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Battery, two small bulbs, two switches, connecting copper wires for classroom activity Background: The purpose of this topic is to revise voltage and current and introduce the devices that measure them: voltmeter and ammeter. It will help the students to understand that voltage and current are measurable quantities that are calculated using devices. At this level, students have no prior knowledge of these devices. Now, they will be introduced to them in detail. Introduction Ask the students: What is the difference between large and small current, low and high voltage? Can it be measured? Write the responses on writing board. Tell the students that today we will be learning about those devices which are used to measure voltage and current in a circuit. (The teacher will announce that today we are going to begin topic 11.3 from 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that while using an electrical circuit, it is important to measure the current that flows through the circuit and the voltage that is developed by a battery or a cell. These measurements are made by the following devices. An ammeter is an instrument that is used to measure the current flowing through a wire of a closed circuit. The ammeter is always connected in series in a wire. The direction of current is taken as the direction of the conventional current. Ammeter gives the value of current in amperes (A) or milli-amperes (mA). A voltmeter is an instrument that is used to measure the voltage developed by the battery in a circuit component of a closed circuit. The voltmeter is always connected in parallel with that component. Voltmeter gives the value of voltage in volts (V) or milli-volts (mV). Classroom Activity (Page 144 on book): To explain the formation and working of series and parallel circuits, follow the activity on page 144 of the book. First connect the cells together and connect two wires with tape at the two ends. Connect an off switch at one end and a wire with the switch’s other end. Now connect the bulbs end to end between the switch and other wire from the cells. Turn the switch on. Both the bulbs will glow. Now connect the bulbs in parallel branches with the cells. Connect a switch in the first 166 Teacher Resource Pack Guide Science 7 branch and a second switch in the second branch. Turn both switches on. Both the bulbs will glow. Now turn the second switch off. The second bulb will turn off but the other will keep glowing. Answers: One bulb keeps glowing because the circuit is parallel and the current has different available paths to flow through. Even if one path is opened, the other remains closed. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 7. What is voltage? What is current? 8. How are they related? What are ammeter and voltmeter? 9. How are they connected in a circuit? Test Exercise – 1 A. 1. 2. 3. 4. 5. B. 1. Ans: 2. Ans: 3. Ans: 4. Ans: Choose the correct answer and fill the circle. The flow of electric charges is called: voltage current resistance electrical energy Load components are connected end to end in a: parallel circuit resistor battery series current Electrical energy is supplied by the: resistor battery voltmeter ammeter Ammeter is always connected in: parallel can be connected in both ways series cannot be connected in either way Voltmeter is always connected in: parallel can be connected in both ways series cannot be connected in either way Answer the following questions briefly. Define electric current, resistance and voltage. The flow of electric charges around the circuit is called electric current. Opposition to the flow of current is called resistance. Work done by the battery on a single charge to move it once through the circuit is called voltage. How do we make a parallel circuit? In a parallel circuit resistors or bulbs are connected in branches that are parallel to each other. What is the purpose of an ammeter? An ammeter is an instrument that is used to measure the current flowing through a wire of a closed circuit. What is the purpose of a voltmeter? A voltmeter is an instrument that is used to measure the voltage developed by the battery in a circuit component of a closed circuit. Lesson 5 Topic: Teaching objectives: 167 (11.4: Effects of Electric Current) ⦁ Recall voltage and current. ⦁ Introduce electric lighting. Teacher Resource Pack Guide Science 7 ⦁ Introduce electric heating. ⦁ Introduce chemical effect. ⦁ Introduce magnetic effect. Key vocabulary: Voltage, current, ampere, heating, lighting, chemical, magnetic. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce the effects that are caused by an electric current. It will help the students to understand that these effects have useful applications. At this level, students have no prior knowledge of these effects. Now, they will be introduced to them in detail. Introduction Ask the students: What is the use of a bulb, an electric heater and a motor? Write the responses on writing board. Tell the students that today we will be learning about the reason behind the working of these appliances. (The teacher will announce that today we are going to begin topic 11.4 from 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that until now, we have studied how electric current can be produced in electrical circuits. Now we will discuss how the effects that an electric current produces are applied to make our lives easier. First, let us discuss these effects. Lighting by bulbs is uses electric current. Electric charges moving at high speeds collide with tungsten atoms when they flow through the tungsten coil of a filament bulb. These collisions increase the temperature of the coil so much that it glows and produces light. Heating effect is also produced by the same principle. Moving charges collide with atoms of the heating element (coil or plate). The charges’ kinetic energy is transferred to the atoms and thus the temperature of the heating element increases. When electric current is passed through a conducting solution(such as salt water), a chemical reaction takes place in the solution. This is called chemical effect of electric current. Current flowing through the solution can create bubbles near the electrodes change of colour of solution etc. When electric current passes through a wire, it behaves like a magnet and attracts metals like iron and steel or moves a compass needle. This is the magnetic effect of the electric current. This effect is used in making temporary magnets called electromagnets. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 10. How is electric lighting produced? How is electric heating produced? 11. What is chemical effect? What is magnetic effect? Lesson 6 Topic: Teaching objectives: (11.5: Uses of Electricity) ⦁ Introduce the uses of electricity. ⦁ Relate the uses with the corresponding effects of electric current. Key vocabulary: Lamp, iron, kettle, stove, electroplating, coat, junkyard. Materials required: Writing board (black or white), chalk, markers, duster 168 Teacher Resource Pack Guide Science 7 CSS Science for class – 7 Background: The purpose of this topic is to introduce the uses of electricity and relate those uses to the effects that are caused by an electric current. It will help the students to understand the relation between the uses and the effects applied in them. At this level, students have no prior knowledge of this relationship. Now, they will be introduced to it in detail. Introduction Ask the students: Name some uses of electricity in daily life. Write the responses on writing board. Tell the students that today we will be learning about the uses of electricity and how they work. (The teacher will announce that today we are going to begin topic 11.5 from 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that the effects produced by electric current are applied in various appliances that run on electricity. Following are some common appliances that make our lives comfortable. The lighting effect of electric current is used in tungsten bulbs (filament lamps) and tube-lights (fluorescent lamps). Heating effect of electric current is used in electric heaters, stoves, kettles and irons. All these appliances contain coils as heating elements which get hot when current flows through them. The process of depositing a layer of a desired metal on any other material by chemical effect of current is called electroplating. Imitation jewelry is made by applying a layer of gold or silver. Applying a layer of chromium on an article by this method is called chrome plating. Parts of bicycle, motorbike and sanitary fittings are chrome plated by this method. Tin cans are made by electroplating tin on iron. The magnetic effect is of a current is used in making electromagnets that are magnetic only when current flows through their coils. Huge electromagnets are a part of cranes that are used to lift heavy metal scrap in junkyards. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 1. Name some uses of electricity. 2. Relate the appliance with the effect of electric current used in it. Lesson 7 Topic: Teaching objectives: (11.6: Hazards of Electricity) (11.7: Safety Devices for Circuits) ⦁ Recall electrocution. ⦁ Introduce overhead power lines, exposed electrical parts, wet conditions, damaged insulation, and overloaded circuit. ⦁ Introduce safety devices: live, neutral and earth, fuse, earthing, three-pin plug, circuit breaker, MCB, ELCB. Key vocabulary: Electrocution, overhead power lines, exposed electrical parts, wet conditions, damaged insulation, overloaded circuit, live, neutral and earth, fuse, earthing, three-pin plug, circuit breaker, MCB, and ELCB. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: 169 Teacher Resource Pack Guide Science 7 The purpose of this topic is to introduce the dangers or hazards of electricity and safety devices used to avoid these hazards. It will help the students to be aware of the hazards of electricity and to learn about the safety devices. At this level, students have no prior knowledge of these hazards and devices. Now, they will be introduced to them in detail. Introduction Ask the students: What is an electric shock? Is it dangerous? Write the responses on writing board. Tell the students that today we will be learning about the hazards of electricity and safety devices that we use. (The teacher will announce that today we are going to begin topic 11.6 from 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that major threat to humans from electricity is electrocution or electric shock. Moving charges in an electric current carry so much energy that if a body is exposed, all the energy is transferred to it. This is extremely harmful, leading to injury, even death. Following are some hazards of electricity. The ways by which we can avoid them have also been mentioned. Overhead power lines are very dangerous. Do not touch or try to contact an overhead power line. Exposed wires or terminals are extremely hazardous and may cause electrocution if touched. Never use a panel that has exposed wires. Wet conditions such as a flooded basement are equally hazardous. Water increases the risk of electric shock because it is a good conductor. Avoid using electric tools in wet locations. Defective or inadequate insulation is a hazard too. It exposes the current carrying copper wires. Therefore, never use tools or extension cords with damaged insulation. Overloaded circuits can cause fire because of blowing of wires due to excess current. To avoid this, use proper fuses or circuit breakers and never overload an outlet. Let us now study some devices that ensure safe use of electricity when used in electrical circuits but let us first understand some essential concepts. To understand their function we should know that for electrical circuits at a large scale, electric current is carried to the load by a wire called the live wire (as in a wire carrying conventional current, which is connected to the positive terminal of the battery in a laboratory circuit). Its colour is red. The return path to the current is provided by the blue neutral wire. The metal casing of the load is connected with the earth wire (green or yellow or both) makes excess charge on the metal casing flow to a conductor called earth. A fuse is used to prevent the flow of excessive current through the circuit. It is a short thin wire connected in series with the positive terminal before the load. It blows when an excess current flows and disconnects the circuit and stops the current. It is replaced after every use. In this way it protects the load and wires from blowing. Fuses are different capacities or fuse ratings such as 1 ampere, 3 ampere, 5 ampere etc. The flow of excess charge from the metal casing of an appliance to a conductor (called earth) is called earthing. This is achieved by a low-resistance wire called the earth wire. This avoids electrocution if the casing is touched. The three-pin plug or fused plug is used for running portable electrical appliances such as an electric kettle. It contains a cartridge fuse and three terminals for live, neutral and earth wires. The fuse is connected in series with the live wire. When an excess current flows through the live wire, the fuse blows and stops the current. Circuit breakers also perform similarly as a fuse does. However we do not need to replace them like a fuse after each use. Instead, its lever is pulled up after it is automatically comes down while breaking the circuit. The automatic function is performed with the help of an electromagnet. The two types used in homes are described as follows. The MCB prevents excessive current flow through the circuit by tripping or breaking it. When the current exceeds its required value the circuit breaker trips. In this way, the MCB cuts off the supply to a part of the 170 Teacher Resource Pack Guide Science 7 house circuit. The ELCB checks the amount of current flowing through the live wire. The current in the neutral wire should remain the same as that in the live wire. If there is a fault, there will be a small current leakage to the earth through the earth wire (or more dangerously, through a person). The ELCB detects this leakage and trips, stopping the current from the live wire. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like: 3. Name some hazards of electricity. 4. Name and describe the working of fuse and circuit breaker. Lesson 8 Topic: (11.8: Household circuits and billing of electricity) Teaching objectives: ⦁ Recall electric circuits. ⦁ Recall series and parallel circuits. ⦁ Introduce household circuitry and electric billing through kilowatt hour. Key vocabulary: Household, billing, kilowatt hour (kWh), meter, main fuse. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce the students to household and commercial use of electricity at a large scale. It will help the students to understand the type of circuits used in homes and the unit used for electric billing. At this level, students have no prior knowledge of these processes. Now, they will be introduced to them in detail. Introduction Ask the students: Have you ever thought how electricity bills are calculated? Write the responses on writing board. Tell the students that today we will be learning about the parallel circuits in our homes and electric billing. (The teacher will announce that today we are going to begin topic 11.8 from 11th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that Electricity is supplied to our homes by power lines which contain the live wire (L) and the neutral wire (N). The current enters through the live wire and returns through the neutral wire. The live wire is at high voltage (240 or 220 V) and the neutral wire is at low voltage (0 V). The wires run through the main fuse box which contains a circuit breaker connected in series with the live wire. Then comes the electricity meter which counts the units consumed. From there the wires go to the household circuit. All the connections are made in parallel. So that if the circuit of say a lamp is switched off or blows, the fan does not stop. Have you ever thought how the cost of electricity consumption is calculated? An electricity meter does this job. But the joule (J), which is the unit of all forms of energy, is not used. It is because joule is too small to be used at a large commercial scale. Instead of joule we use the kilowatt hour (kWh). It is a large unit and also includes the time duration in hours in which electricity is used. The electricity meter gives a reading during a month. It is noted by the meter-reader. When he comes after a month and takes the new reading, the supply company 171 Teacher Resource Pack Guide Science 7 subtracts the previous reading from the latest reading. Then the number of kilowatt hours is multiplied by the price of one kilowatt hour which is decided by the authorities. To explain electric billing by kilowatt hour, follow worked example 11.2 on page 151. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like: 5. What type of circuits is used in homes? Why is kilowatt hour used in billing? 6. Review Exercise A. 1. Choose the correct answer and fill the circle: Electric current in metals is due to the flow of: protons electrons both protons and electrons nuclei 2. Which of the following statements is correct about parallel circuits? appliances are connected end to end same energy is supplied to all the appliances same current is supplied to all the appliances all the appliances switch off when one of them is switched off 3. A resistor offers opposition to the flow of current by collision between the charge carriers and its atoms. Which form of energy is the kinetic energy of the charge carriers converted into? chemical energy heat light sound 4. Pick the correct order of quantities measured by a voltmeter and an ammeter respectively. voltage, current current, voltage resistance, energy current, energy 5. Electric current can be used: only in light bulbs as a source of chemical reactions only as a magnet to produce lighting, heating, magnetic effect, and chemical effect. 6. Junkyard magnets: use the heating effect of electric current use the magnetic effect of electric current use the chemical effect of electric current are made of natural magnets 7. Which of the following carries excess charge away from the metal casing of an appliance? live wire natural wire earth wire fuse 8. The three-pin plug does not contain: a fuse an earth wire a circuit breaker a cord grip 9. Which of the following monitors the leakage current? earth wire MCB ELCB fuse 10. The fan does not turn on if we only turn on the light. This is because: the fan is always faulty they are connected in series they are connected in parallel only one of them can be turned on at the same time B. Answer the following questions shortly. 1. Differentiate between conventional current and electronic current. Ans: We take the direction of flow of current from the positive terminal to the negative terminal of the battery. Current flowing in this direction is called conventional current. 172 Teacher Resource Pack Guide Science 7 Flow of electrons is from the negative to the positive terminal. This is called electronic current. 2. What are the four basic components of an electric circuit? Ans: Electric circuit usually consists of four main components: A source of electrical energy that drives the charges (battery or cell) A load on which the charges do some useful job (bulb, motor etc.) Electrical conductors to connect the components (copper wires) Switch to open or close the circuit 3. What do voltage and resistance signify? Ans: The battery drives the electrical charges. To move the charges a battery does work on them. Work done by the battery on a single charge to move it once through the circuit is called voltage. Its symbol is V and is measured in volts (V). As the charge particles move through a wire of an electrical circuit, they collide with the atoms of the wire’s material. This produces an opposition to the flow of current which is called resistance. It produces heat. 4. Name the energy conversions in an electrical circuit that contains a bulb. Ans: Energy conversions are chemical to electrical to kinetic to light and heat. 7. Draw the symbols of various electrical components. Ans: 6. How is electricity hazardous? Ans: Major threat to humans from electricity is electrocution or electric shock. That is how electricity hazardous. 7. How is overloading of circuits dangerous? Ans: Overloaded circuits can cause fire because of blowing of wires due to excess current. 8. Differentiate between the live wire and the neutral wire. 173 Teacher Resource Pack Guide Science 7 Ans: Electric current is carried to the load by a wire called the live wire (as in a wire carrying conventional current, which is connected to the positive terminal of the battery in a laboratory circuit). Its colour is red. The return path to the current is provided by the blue neutral wire. 9. Compare the workings of an MCB and an ELCB. Ans: The MCB prevents excessive current flow through the circuit by tripping or breaking it. When the current exceeds its required value, the circuit breaker trips. In this way, the MCB cuts off the supply to a part of the house circuit. The ELCB checks the amount of current flowing through the live wire. The current in the neutral wire should remain the same as that in the live wire. If there is a fault, there will be a small current leakage to the earth through the earth wire (or more dangerously, through a person). The ELCB detects this leakage and trips, stopping the current from the live wire. 10. What is the purpose of the kilowatt hour? Ans: The joule is too small to be used at a large commercial scale. Instead of joule we use the kilowatt hour (kWh). It is a large unit and also includes the time duration in hours in which electricity is used. C. Answer the following questions in details. 1. Explain the different effects produced by electric current and their applications. Ans: Effects of Electric Current: The effects that an electric current produces are applied to make our lives easier. Let us discuss these effects. Lighting Effect: Lighting by bulbs is uses electric current. Electric charges moving at high speeds collide with tungsten atoms when they flow through the tungsten coil of a filament bulb. These collisions increase the temperature of the coil so much that it glows and produces light. Heating Effect: Heating effect is also produced by the same principle. Moving charges collide with atoms of the heating element (coil or plate). The charges’ kinetic energy is transferred to the atoms and thus the temperature of the heating element increases. Chemical Effect: When electric current is passed through a conducting solution (such as salt water), a chemical reaction takes place in the solution. This is called chemical effect of electric current. Current flowing through the solution can create bubbles near the electrodes change of colour of solution etc. Magnetic Effect: When electric current passes through a wire, it behaves like a magnet and attracts metals like iron and steel or moves a compass needle. This is the magnetic effect of the electric current. This effect is used in making temporary magnets called electromagnets. 2. Write detailed notes on the following. a. Voltage and resistance b. Series and parallel circuits c. Voltmeter and ammeter Ans: a) Voltage and Resistance: The battery drives the electrical charges. To move the charges a battery does work on them. Work done by the battery on a single charge to move it once through the circuit is called voltage. Its symbol is V and is measured in volts (V). As the charge particles move through a 174 Teacher Resource Pack Guide Science 7 wire of an electrical circuit, they collide with the atoms of the wire’s material. This produces an opposition to the flow of current which is called resistance. It produces heat. “The opposition offered to the flow of current is called resistance.” It is symbolized as ‘R’ and is measured in ohms (Ω). Besides the resistance offered by the wires, we can also limit the flow of current according to our own requirement. This is achieved by using circuit components called resistors. Relationship between Voltage and Resistance: Voltage of a battery and resistance of a conductor through which electric charges flow is given by the following mathematical formula. V = IR Here V, I and R represent the voltage, the current and the resistance respectively. Usually the resistance remains fixed. In that case, increasing the voltage increases the current. b) Series and Parallel Circuits: Electrical circuits are classified into two main types according to the arrangement of the components that make the load (resistors, bulbs, motor etc.) These types are series circuit and parallel circuit. In a series circuit, all the components are connected end to end (in a line). That is, they make a single loop or path of current to form the circuit. On the other hand, in a parallel circuit resistors or bulbs are connected in branches that are parallel to each other. Multiple loops or paths of current are formed in a parallel circuit. Current is divided among the appliances but energy supplied to each appliance remains the same. Disadvantage of the Series Circuit: The same current flows through all the components of a series circuit due to single path of flow. This means that if one of the components is destroyed due to some reason, current through the whole circuit stops. c) Voltmeter and Ammeter: While using an electrical circuit, it is important to measure the current that flows through the circuit and the voltage that is developed by a battery or a cell. These measurements are made by the following devices. Voltmeter: A voltmeter is an instrument that is used to measure the voltage developed by the battery in a circuit component of a closed circuit. The voltmeter is always connected in parallel with that component. Voltmeter gives the value of voltage in volts (V) or milli-volts (mV). Ammeter: An ammeter is an instrument that is used to measure the current flowing through a wire of a closed circuit. The ammeter is always connected in series in a wire. The direction of current is taken as the direction of the conventional current. Ammeter gives the value of current in amperes (A) or milli-amperes (mA). 3. Explain different hazards of electricity and the precautions to avoid them. Ans: Hazards of Electricity: Major threat to humans from electricity is electrocution or electric shock. Moving charges in an electric current carry so much energy that if a body is exposed, all the energy is transferred to it. This is extremely harmful, leading to injury, even death. Following are some hazards of electricity. The ways by which we can avoid them have also been mentioned. Overhead Power Lines: Overhead power lines are very dangerous. Do not touch or try to contact an overhead power line. 175 Teacher Resource Pack Guide Science 7 Exposed Electrical Parts: Exposed wires or terminals are extremely hazardous and may cause electrocution if touched. Never use a panel that has exposed wires. Wet Conditions: Wet conditions such as a flooded basement are equally hazardous. Water increases the risk of electric shock because it is a good conductor. Avoid using electric tools in wet locations. Damaged Insulation: Defective or inadequate insulation is a hazard too. It exposes the current carrying copper wires. Therefore, never use tools or extension cords with damaged insulation. Overloaded Circuit: Overloaded circuits can cause fire because of blowing of wires due to excess current. To avoid this, use proper fuses or circuit breakers and never overload an outlet. 4. Explain the working of different safety devices used in household circuits. Ans: Safety Devices for Circuits: Some devices that ensure safe use of electricity when used in electrical circuits are as follows. Live, Neutral and Earth: To understand their function we should know that for electrical circuits at a large scale, electric current is carried to the load by a wire called the live wire (as in a wire carrying conventional current, which is connected to the positive terminal of the battery in a laboratory circuit). Its colour is red. The return path to the current is provided by the blue neutral wire. The metal casing of the load is connected with the earth wire (green or yellow or both) makes excess charge on the metal casing flow to a conductor called earth. Fuse: A fuse is used to prevent the flow of excessive current through the circuit. It is a short thin wire connected in series with the positive terminal before the load. It blows when an excess current flows and disconnects the circuit and stops the current. It is replaced after every use. In this way it protects the load and wires from blowing. Fuses are different capacities or fuse ratings such as 1 ampere, 3 ampere, 5 ampere etc. Earthing: The flow of excess charge from the metal casing of an appliance to a conductor (called earth) is called earthing. This is achieved by a low-resistance wire called the earth wire. This avoids electrocution if the casing is touched. Three-pin Plug: The three-pin plug or fused plug is used for running portable electrical appliances such as an electric kettle. It contains a cartridge fuse and three terminals for live, neutral and earth wires. The fuse is connected in series with the live wire. When an excess current flows through the live wire, the fuse blows and stops the current. Circuit Breakers: Circuit breakers also perform similarly as a fuse does. However we do not need to replace them like a fuse after each use. Instead, its lever is pulled up after it is automatically comes down while breaking the circuit. The automatic function is performed with the help of an electromagnet. The two types used in homes are described as follows. Miniature Circuit Breaker (MCB): 176 Teacher Resource Pack Guide Science 7 The MCB prevents excessive current flow through the circuit by tripping or breaking it. When the current exceeds its required value, the circuit breaker trips. In this way, the MCB cuts off the supply to a part of the house circuit. Earth Leakage Circuit Breaker (ELCB): The ELCB checks the amount of current flowing through the live wire. The current in the neutral wire should remain the same as that in the live wire. If there is a fault, there will be a small current leakage to the earth through the earth wire (or more dangerously, through a person). The ELCB detects this leakage and trips, stopping the current from the live wire. 5. Explain the step by step process of flow of electric current through a household circuit. Ans: Electricity is supplied to our homes by power lines which contain the live wire (L) and the neutral wire (N). The current enters through the live wire and returns through the neutral wire. The live wire is at high voltage (240 or 220 V) and the neutral wire is at low voltage (0 V). The wires run through the main fuse box which contains a circuit breaker connected in series with the live wire. Then comes the electricity meter which counts the units consumed. From there the wires go to the household circuit. All the connections are made in parallel. So that if the circuit of say a lamp is switched off or blows, the fan does not stop. D. Solve the following numerical problems using calculator. 1. The voltage through a conductor is 220 V. A current of 10 amperes flows through it. What is the value of its resistance in ohms (Ω)? Given that, Voltage = V = 220 volt Current = I = 10 ampere To be found, Resistance = R = ? Formula to be used, 𝑉 = 𝐼𝑅 Calculation: 𝑉 𝑅= 𝐼 220 𝑅= 10 2. 𝑅 = 22 𝑜ℎ𝑚𝑠 The price of one kilowatt hour is Rs. 12. If the units consumed for March are 550 kilowatt hours, what will be the total cost of electricity used in March? Given that, Price of 1 kilowatt hour (kWh) = P = Rs. 12 Consumed units during the month of March = N = 550 To be found, Cost of Electricity = C = ? Formula to be used, 𝐶 = 𝑁 ×𝑃 Calculation: 𝐶 = 550 × 12 𝐶 = 𝑅𝑠. 6600 177 Teacher Resource Pack Guide Science 7 Unit # 12 INVESTIGATION THE SPACE Lesson 1 Topic: (12.1: Beyond the Solar System) (12.2: The big bang and the origin of the universe) Teaching objectives: ⦁ Introduce the concept of galaxy and give the number of galaxies. ⦁ Introduce the big bang theory of the origin of the universe. ⦁ Explain the evidence of the big bang theory. Key vocabulary: Galaxy, celestial, big bang, cosmic, microwave. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this unit is to introduce the galaxies, stars, the big bang theory and other related concepts of space. At this level, students have no prior knowledge of these concepts. Now, they will be introduced to them in detail. Introduction Ask the students: Can you recall what is meant by heavenly bodies? Can you name some of them? Write the responses on writing board. Tell the students that today we will build on our previous knowledge of space. (The teacher will announce that today we are going to begin 12th chapter from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that in the last chapter of this book, we will conclude our exploration of science with the study of space beyond our planet. We are already familiar with celestial bodies such as stars, planets, moons, asteroids etc. In this chapter we will go one step further in studying space and discuss galaxies, stars, and black holes in detail. Our universe is both ancient and vast, and expanding out farther and faster every day. It consists of galaxies, stars, planets, black holes and other celestial bodies. The universe is so vast that it contains over 200 billion galaxies with an average of 200 billion stars each. These galaxies are separated by so large a distance that even light (which travels at the fastest observable speed of 3x108 meters per second) takes millions of years to travel from one galaxy to another. Although there are other theories that try to explain how the universe came into being but the most prevailing model is the Big Bang Theory. The theory tells us that the whole universe was contained in an extremely small point which had infinite density (mass per unit volume) and extremely high temperature. Due to this extreme hotness, a huge explosion occurred which is called the big bang. Ever since the big bang, the universe is expanding at a very fast rate. This claim is supported by evidence like movement of galaxies away from each other and cosmic microwave background radiation (travelling of energy from the big bang in the form of microwaves). Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 12. How many galaxies are there in the universe? 13. What is meant by the big bang theory? 178 Teacher Resource Pack Guide 14. Science 7 What are the evidences used for the big bang theory? Lesson 2 Topic: Teaching objectives: (12.3: Celestial Bodies) ⦁ Introduce the life cycle of stars. ⦁ Introduce cosmic distance and light year. ⦁ Introduce galaxy and explain its types. ⦁ Introduce black holes and explain their formation Key vocabulary: Supernova, red giant, supergiant, white dwarf, light year, spiral, irregular, elliptical, Milky Way, black hole. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7 Background: The purpose of this topic is to introduce the celestial bodies that is, stars, galaxies and black holes. At this level, students have some prior knowledge of these concepts. Now, they will be introduced to them and the concept of a light year in detail. Introduction Ask the students: What is a star? Do stars form groups? Write the responses on writing board. Tell the students that today we will build on our previous knowledge of stars by studying their life cycles and also about galaxies and their types. (The teacher will announce that today we are going to begin topic 12.3 of 12th chapter from CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that celestial bodies or heavenly bodies are objects in space such as the sun, moon, planets and stars. Stars emit light while the moon and planets like Earth reflect light. They form a part of the vast universe we live in and are usually very far from us. The night sky is dotted with such objects and when we observe them using a telescope they reveal fascinating worlds of their own. Because they are so far away, we cannot see all of them using the naked eye. So we need to rely on telescopes to study them. In this section we shall discuss celestial bodies such as stars, galaxies and black holes. Stars are giant balls of hot gases that can produce their own light. Stars give out energy by converting Hydrogen gas into Helium in their cores. Stars are gigantic in size and have immense gravitational attraction. The sun is a medium sized star that gives us energy and makes life on earth possible. Stars are formed in clouds of gas and dust, known as nebula. Nuclear reactions at the center (or core) of stars provides enough energy to make them shine brightly for many years. The exact lifetime of a star depends on its size. Very large, massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years. Smaller stars last for several billion years, because they burn their fuel much more slowly. Eventually the hydrogen fuel that powers the nuclear reactions within stars run out, and they enter the final phases of their lifetime. Over time, they expand, cool and change colour to become red giants. The path they follow beyond that depends on the mass of the star. They explode into a supernova if they are massive. Otherwise, they explode to form a new nebula. Stars are formed, or are "born", in large clouds of gas and dust. The cloud slowly shrinks and then starts to collapse onto a number of points (or cores) within the cloud, all due to the pull of gravity. Small stars, like the Sun, undergo a relatively peaceful death. They pass through a planetary nebula phase to become a white dwarf after its nuclear fuel ends. The universe is so vast that the distances between stars and between galaxies cannot be written conveniently in the tradition units of length such as kilometers. To avoid this difficulty we have devised a unit of distance at the scale of the universe. This unit is called 179 Teacher Resource Pack Guide Science 7 “Light-year.” “One light-year is the distance covered by light in one year.” Galaxies are large groups of stars held together by gravity. The sun and the solar system is part of a galaxy known as the Milky Way. Other galaxies are usually so far away that they look like stars in the night sky. Our neighbouring galaxy, Andromeda, can be seen with naked eye on a clear night. There are three main types of galaxies: Spiral, Elliptical, and Irregular. Spiral galaxies resemble sparling pinwheels. Stars whirl around a massive center by making the arms of the galaxy. Elliptical galaxies have the shape of an ellipse, giving them an elliptical appearance from every angle. We live in one of the arms of a large spiral galaxy called the Milky Way. The Sun and its planets (including Earth) lie in this part of the galaxy, about halfway out from the center. The Milky Way is shaped like a huge whirlpool that rotates once every 200 million years. It is made up of at least 100 billion stars, as well as dust and gas. It is so big that light takes 100,000 years to travel from one side to the other. The center of the Galaxy is very hard to see because clouds of gas and dust block our view. Scientists think that it contains a supermassive black hole that swallows anything passing too close. A black hole is a place in space where gravity pulls so much that even light cannot get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star dies. Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. These special tools can see how stars that are very close to black holes act differently than other stars. When the nuclear fuel of an extremely massive star runs out, it collapses in upon itself under its own gravity. The star explodes into a supernova. If the core remaining after the supernova is very massive, no known repulsive force inside a star can push back hard enough to prevent gravity from collapsing the core into a black hole. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 15. What happens to stars after they die? How many types do galaxies have? 16. How are black holes formed? Lesson 3 Topic: Teaching objectives: (12.4: Looking at Stars) ⦁ Introduce constellations and their purpose. ⦁ Recall the use of a telescope and explain its principle. ⦁ State the precautions for observing the sun. Key vocabulary: Constellation, telescope, concave, lens, magnify, eclipse. Materials required: Writing board (black or white), chalk, markers, duster, CSS Science for class – 7. Background: The purpose of this topic is to introduce the major constellations and basic methods of observing stars. At this level, students have some prior knowledge of these concepts such as a telescope. Now, they will be introduced to them in detail. Introduction Ask the students: Have they ever seen patterns of stars in the night sky? Why is dangerous to look at the sun? Write the responses on writing board. Tell the students that today we will build on our previous knowledge of telescopes and use it to describe methods of observation of space. (The teacher will announce that today we are going to begin topic 12.4 from the 12th chapter of CSS Science 7 book and write the name of chapter and topic on the board.) Explanation Now, teacher will explain to the students that Man has come a long way in space exploration since the time of Galileo Galileo. We have made advanced telescopes and 180 Teacher Resource Pack Guide Science 7 observatories to look at and study the properties and movement of celestial bodies. In this section we shall study what can we observe about space with naked eye and telescopes. A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere. Typical constellations represent animals, mythological people or gods, mythological creatures, or manufactured devices. They can be seen with naked eyes at night. There are 88 modern constellations. Important ones include Centaurus, Leo etc. They help in navigation and seafaring. Other constellations visible at night are: Virgo, Libra, Ursa Major, the big bear etc. Advanced space exploration is not possible with naked eye because of very large distances between other celestial bodies and the Earth. Therefore a telescope is used to view images of objects at long distances in the sky such as the moon and the stars. A simple telescope uses two mirrors to reflect light towards the eye. One mirror at the back is curved and concave. It bends the incident rays inward towards the second mirror at the center of the telescope. This mirror is held at 450. It reflects the rays of light coming from the curved mirror towards the eye. Never use a telescope or binoculars to look at the Sun. If pointed directly. The lens of the telescope focuses a lot of light from the Sun towards the eye. Even a glimpse of the Sun through the telescope can cause irreversible eye damage or permanent blindness. Instead focus the rays from a telescope on a piece of paper. Solar eclipses should be observed by using eclipse glasses. Conclusion In last 5-10 minutes, recall the lesson by asking questions from students like. 17. What is a constellation? 18. Why is it helpful to define constellations? 19. What is the basic principle of a telescope? 20. What precaution must be taken to observe the sun? Review Exercise A. 1. 2. 3. 4. 5. 6. 7. Choose the correct answer and fill the circle. An average-sized star becomes a: red giant nebula blue giant red super-giant Stars are: non-luminous objects luminous objects transparent objects opaque objects Which of the following statements is correct about the Milky Way? it is a black hole it is elliptical in shape. it is an irregular galaxy it contains a supermassive black hole at its center. Which of the following galaxies contains arms? elliptical irregular spiral none Black holes are produced: when a small star collapses before a supernova of a massive star after a supernova of a massive star during the life of a small star Which of the following groups represent constellations? Earth, Mars and Jupiter Andromeda and Milky way Virgo, Libra and Leo The Sun and the Moon The mirror used at the rear end of a telescope is made: plane convex concave refracting 181 Teacher Resource Pack Guide Science 7 B. Answer the following questions briefly. 1. Differentiate between a star and a galaxy. Ans: Stars are giant balls of hot gases that can produce their own light whereas galaxies are large groups of stars held together by gravity. 2. Differentiate between a star and a planet. Ans: Stars are giant balls of hot gases that can produce their own light whereas planets are bodies that orbit stars. 3. What does the Big Bang stand for? Ans: The Big Bang stands for the huge explosion after which the universe was created. 4. Describe the major types of galaxies. Ans: There are three main types of galaxies: Spiral, Elliptical, and Irregular. Spiral galaxies resemble spiraling pinwheels. Stars whirl around a massive center by making the arms of the galaxy. Elliptical galaxies have the shape of an ellipse, giving them an elliptical appearance from every angle. Irregular galaxies have no definite shape. 5. What is a black hole? Ans: A black hole is a place in space where gravity pulls so much that even light cannot get out. The gravity is so strong because matter has been squeezed into a tiny space. 6. Describe the shape of the Milky Way. Ans: The Milky Way has a spiral shape with many arms. 7. What will happen to the Sun after its nuclear fuel runs out? Ans: The sun will become a white dwarf. 8. What does the word Constellation mean? Ans: Constellation means a pattern of stars in the sky that resembles any object. 9. What happens when we point the telescope at the Sun and observe it directly? Ans: It causes eye damage due to the focusing of a lot of light towards the eye. 10. Why is the mirror at rear end of a telescope made curved? Ans: The mirror is curved to focus the light towards the eye. C. Answer the following questions in details. 1. Write a note on the Big Bang Theory and the evidence that supports it. Ans: Although there are other theories that try to explain how the universe came into being but the most prevailing model is the Big Bang Theory. The theory tells us that the whole universe was contained in an extremely small point which had infinite density (mass per unit volume) and extremely high temperature. Due to this extreme hotness, a huge explosion occurred which is called the big bang. Evidence: Ever since the big bang, the universe is expanding at a very fast rate. This claim is supported by evidence like movement of galaxies away from each other and cosmic microwave background radiation (travelling of energy from the big bang in the form of microwaves). 2. Explain the life cycle of stars of different sizes. Ans: Stars are formed in clouds of gas and dust, known as nebula. Nuclear reactions at the center (or core) of stars provides enough energy to make them shine brightly for many years. The exact lifetime of a star depends on its size. Very large, massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years. Smaller stars last for several billion years, because they burn their fuel much more slowly. Eventually the hydrogen fuel that powers the nuclear reactions within stars run out and they enter the final phases of their lifetime. Over time, they expand, cool and 182 Teacher Resource Pack Guide Science 7 change colour to become red giants. The path they follow beyond that depends on the mass of the star. They explode into a supernova if they are massive. Otherwise, they explode to form a new nebula. 3. Explain how is a black hole is formed. Ans: A black hole is a place in space where gravity pulls so much that even light cannot get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star dies. When the nuclear fuel of an extremely massive star runs out, it collapses in upon itself under its own gravity. The star explodes into a supernova. If the core remaining after the supernova is very massive, no known repulsive force inside a star can push back hard enough to prevent gravity from collapsing the core into a black hole. 4. Explain the working principle of a telescope. Ans: Advanced space exploration is not possible with naked eye because of very large distances between other celestial bodies and the Earth. Therefore a telescope is used to view images of objects at long distances in the sky such as the moon and the stars. A simple telescope uses two mirrors to reflect light towards the eye. One mirror at the back is curved and concave. It bends the incident rays inward towards the second mirror at the center of the telescope. This mirror is held at 45°. It reflects the rays of light coming from the curved mirror towards the eye. 5. Describe the three major types of galaxies. Also write a note on Milky Way. Ans: Galaxies are large groups of stars held together by gravity. The sun and the solar system is part of a galaxy known as the Milky Way. Other galaxies are usually so far away that they look like stars in the night sky. Our neighboring galaxy, Andromeda, can be seen with naked eye on a clear night. Types of Galaxies: There are three main types of galaxies: Spiral, Elliptical, and Irregular. Spiral galaxies resemble spiraling pinwheels. Stars whirl around a massive center by making the arms of the galaxy. Elliptical galaxies have the shape of an ellipse, giving them an elliptical appearance from every angle. Irregular galaxies have no definite shape. Milky Way: We live in one of the arms of a large spiral galaxy called the Milky Way. The Sun and its planets (including Earth) lie in this part of the galaxy, about halfway out from the center. The Milky Way is shaped like a huge whirlpool that rotates once every 200 million years. It is made up of at least 100 billion stars, as well as dust and gas. It is so big that light takes 100,000 years to travel from one side to the other. The center of the Galaxy is very hard to see because clouds of gas and dust block our view. Scientists think that it contains a supermassive black hole that swallows anything passing too close. Model Paper No. 1 Section – A: Multiple Choice Questions Marks: 40 Roll No. __________ Choose the correct option. 1. Epiglottis is present above: pharynx esophagus 183 Time: 50 Minutes 40 oral cavity trachea Teacher Resource Pack Guide 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. Science 7 The digested food is absorbed in: small intestine large intestine stomach mouth When we inhale, the diaphragm: contracts relaxes does not move open Salivary amylase performs the digestion of: carbohydrates fats proteins lipids Hydrochloric acid is secreted into: mouth small intestine large intestine stomach The place where exchange of food, oxygen and wastes occur in human body is: vein arteries capillaries lymph vessels The red colour of blood due to: clot formation oxygenation deoxygenation dirt particles The structure that transfers the sperm present in pollen to the ovary is: stigma cotyledon seed pollen tube The upper part of ovary in a flower is called: stigma filament anther ovule The fungi reproduce through: layering fragmentation cutting spore formation Which of the following is the characteristics of Asexual reproduction? it involves two parents it involves only one parent It is a slow process the offerings formed have same variations Bacteria and fungi are: posers producers predators grazers The white fur of polar bear is its adaptation against: scarcity of water scarcity of food predators none of these Searching for food at night is adaptation against: predators food shortage water shortage climatic severity Decomposers provide nutrients to: animals plants soil all of these The rain water which is stored in the soil is known as: green water blue water white water yellow water In turbid water level of which gas is low? dissolved oxygen dissolved nitrogen dissolved carbon dioxide dissolved chlorine Unwanted gases in water are removed through the process of: aeration coagulation sedimentation chlorination How many protons Zn = 30 has: 27 28 29 30 Browning of apple is due to reaction wit: carbon dioxide oxygen sulphur nitrogen A metal pot of water is being heated on a stove. Which of the following process is NOT happening? conduction convection radiation evaporation A vacuum flask prevents: conduction convection radiation all of these During a convection current, which of the following does not happen? 184 Teacher Resource Pack Guide 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. Science 7 hot air sinks hot air rises cold air sinks particles move Which of the following combinations represents primary colours? red, yellow, blue red, purple, blue red, green, blue red, orange, green An opaque object is coloured because of: absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one Total internal reflection occurs: at critical angle after critical angle at the normal in the rare medium Which of the following statements is not correct about the loudness of a sound? it depends on frequency loudness depends on amplitude decreasing the area of the vibrating object decreases loudness increasing the area of the vibrating object increases loudness Which of the following monitors the leakage current? earth wire MCB ELCB fuse The fan does not turn on if we only turn on the light. This is because: the fan is always faulty they are connected in series they are connected in parallel only one of them can be turned on at the same time Junkyard magnets: use the heating effect of electric current use the magnetic effect of electric current use the chemical effect of electric current are made of natural magnets Electric current in metals is due to the flow of: protons electrons nuclei reflection both protons and electrons Which of the following statements is not correct about a galaxy? it may have different shapes it contains black holes it contains moons light can travel across it in just a year Which of the following statements is correct about the Milky Way? it is a black hole it contains a supermassive black hole at its center it is elliptical in shape it is an irregular galaxy Which of the following galaxies contains arms? elliptical irregular spiral none Black holes are produced: when a small star collapses before a supernova of a massive star after a supernova of a massive star during the life of a small star The claim of the big bang is supported by: expansion of the universe cosmic microwave background both expansion and cosmic microwave background evolution of life on Earth Which of the following groups represent constellations? Earth, Mars and Jupiter Virgo, Libra and Leo Andromeda and Milky way The Sun and the Moon The mirror used at the rear end of a telescope is made: plane convex concave refracting Electric current in metals is due to the flow of: protons electrons nuclei both protons and electrons Which of the following statements is correct about parallel circuits? 185 Teacher Resource Pack Guide Science 7 appliances are connected end to end same current is supplied to all the appliances same energy is supplied to all the appliances all the appliances switch off when one of them is switched off Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) Define digestion. (1) (b) Name the nutrient that each below given substance helps to digest: (3) (i) Salivary amylase (ii) bile (iii) pancreatic juice (c) Describe the importance of digestion. (2) Q.2: (a) Define desert habitat. (2) (b) What are the peculiar features of deserts? (2) (c) Describe at least two adaptations of animals and plants living in deserts. (2) Q.3: Define transpiration. (1) (b) How does the structure of a leaf help in movement of materials? (3) (c) Draw the structure of leaves showing movement of material movement. (1) Q.4: (a) Draw flow sheet diagram of water treatment process. (4) (b) Differentiate between “purified water” and “distilled water”. (2) Q.5: (a) What will be the number of protons in an element X that have 30 neutrons and itsmass number is 56. (2) (b) Who discovered the nucleus of an atom? (1) (c) Identify physical or chemical changes also give season for identification. (3) Solubility Combustion Distillation Q.6: (a) How does a solid conduct heat? (2) (b) Write a detailed note on the differences between conduction, convection and radiation. (4) Q.7: (a) What do voltage and resistance signify? (2) (b) What causes refraction? (2) (c) How is electricity hazardous? (2) Q.8: (a) How does a swimming pool appear less deep? (2) (b) Explain the working of different safety devices used in household circuits. (4) Q.9: (a) Compare the working of an MCB with an ELCB. (2) (b) Write a detailed note on refraction, its cause and its occurrence in the environment.(4) Q.10: (a) Describe the shape of the Milky Way. (2) (b) Explain the life cycle of stars of different sizes. (4) Model Paper No. 2 Section – A: Multiple Choice Questions Marks: 40 Time: 50 Minutes Roll No. __________ Choose the correct option. 40 1. The increased in frequency of bowel movement is termed as: stomach ulcer constipation diarrhea acidity 2. The process of responsible for movement of food in digestive tract is: breathing blood circulation peristalsis omitting 3. The excess amount of bile is stored in: pancreases liver gall bladder large intestine 186 Teacher Resource Pack Guide 4. Science 7 During exhalation, the diaphragm moves: upward down ward right ward left ward 5. Blood is carried away from the heart through: ureters veins arteries nerves 6. Which of the following process is responsible for the movement and prepared food in plants body? osmosis diffusion transpiration translocation 7. The deoxygenated blood from the upper part of the body is collected in: superior vena cava inferior vena cava pulmonary artery pulmonary vein 8. Asexual reproduction involves: two gametes only male sex cells fertilization a single parent plant 9. Pollen grain attach themselves to: stigma style ovary filament 10. What happens when a pollinator visit a flower? it eats the pollen it hides pollen it drops down the pollen pollen grains got stick to its body 11. Pollination and fertilization are the part of: asexual reproduction vegetative propagation spore formation sexual reproduction 12. If five food chains are inter connected, they form: energy cycle food cycle food web energy flow 13. Producers are capable of / to: catalysis photosynthesis be decomposers none of these 14. The basic functional unit of the environment is: habitat environment ecosystem blame 15. The feature that most of the aquatic plants have is: air spare less stomata thin leaves thick plant surface 16. The biggest lake on earth. Lake Hunza Lake Baikal Lake Superior Lake Erie 17. The relation that describes the mass of proton is to that of electrons. 1837 times greater 1837 times smaller 7381 times greater 7381 times smaller 18. The outer most shell of 12Mg is: k=2 l=2 m=2 n=2 19. Sublimation is a: physical change chemical change electrical change none 20. Formula of Ammon is: NH3 N N3H Na N2H2 Ne NH 21. Iron A vacuum flask prevents: conduction convection radiation all of these 22. Which of the following processes result from convection? gliding of birds gliding of pilots both of these expansion of concrete 187 Teacher Resource Pack Guide 23. Science 7 To reverse the flow of heat one must: put the hot body close to the cold body keep both bodies hot keep both bodies cold none of these 24. During a convection current, which of the following does not happen? hot air sinks hot air rises cold air sinks particles move 25. Which of the following options correctly relates the mode of transfer of heat with the natural process? conduction, greenhouse effect convection, solar radiation, solar energy convection, greenhouse effect 26. A metal pot of water is being heated on a stove. Which of the following process is NOT happening? conduction convection radiation evaporation 27. A sound wave moves the particles: up and down back and forth in circles with itself 28. Which of the following combinations represents primary colours? red, yellow, blue red, purple, blue red, green, blue red, orange, green 29. Rainbow in the sky is caused by: prism winds lightning water droplets 30. An opaque object is coloured because of: absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one 31. Motion sensing security alarms detect: sound waves longitudinal waves radio waves infrared radiation 32. A prism based periscope is better because: it produces a clear, magnified image prisms do not rust like aluminum coated mirrors both of these prisms disperse light 33. Total internal reflection occurs: at critical angle after critical angle at the normal in the rare medium 34. After the transfer of heat from the hot body to cold body, the cold body: gets warmer than the hot body becomes equal in temperature to the hot body gets colder than the hot body does not absorb heat at all 35. The principle of a reflecting prism is: reflection refraction dispersion total internal reflection 36. A denser medium refracts light because: light stops in the denser medium light changes colour in the denser medium light is converted into sound light changes speed in the denser medium 37. Which of the following statements is correct about parallel circuits? appliances are connected end to end same current is supplied to all the appliances same energy is supplied to all the appliances all the appliances switch off when one of them is switched off 38. Which of the following groups represent constellations? 188 Teacher Resource Pack Guide 39. 40. Science 7 Earth, Mars and Jupiter Virgo, Libra and Leo Andromeda and Milky way The Sun and the Moon The claim of the big bang is supported by: expansion of the universe cosmic microwave background both expansion and cosmic microwave background evolution of life on Earth Which of the following galaxies contains arms? elliptical irregular spiral none Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) Name all the organs of digestive system. (1) (b) Describe the function of small intestine. (4) (c) Name the parts of small intestine. (1) Q.2: (a) Draw and label the structure of heart. (4) (b) Write a note on angioplasty. (2) Q.3: (a) What is reproduction? Why is it important? (2) (b) Differentiate between sexual and asexual reproduction? (2) (c) What do you know about vegetative propagation? (2) Q.4: (a) What are the effects of impurities on water quality? (3) (b) How would you identify a chemical change? (3) Q.5: (a) Write the name of this compound. (1) (b) Guess the valency of each atom in this compound. (1) (c) Mention the ions formed in this compound. (2) (d) Make the ionic structure of its ions showing the electronic distribution in its orbits. (2) Q.6: (a) Why is the mirror at rear end of a telescope made curved? (2) (b) Explain the working principle of a telescope. (4) Q.7: (a) Name the energy conversions in an electrical circuit that contains a bulb. (2) (b) Describe the process of radio transmission? (2) (c) What does the refractive index tell us? (2) Q.8: (a) Differentiate between a star and a galaxy. (2) (b) Explain how a black hole is formed. (4) Q.9: (a) What causes ringing in telephone sets? (2) (b) Write a detailed note on refraction, its cause and its occurrence in the environment. (4) Q.10: (a) What is the purpose of the kilowatt hour? (2) (b) Explain the step by step process of flow of electric current through a household circuit. (4) Model Paper No. 3 Section – A: Multiple Choice Questions Marks: 40 Roll No. __________ Choose the correct option. 40 189 Time: 50 Minutes Teacher Resource Pack Guide 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. Science 7 The place from where gases are exchanged between blood and lungs is: blood vessels bronchi trachea alveoli The windpipe is also called: trachea larynx pharynx epiglottis The stomach produces the enzyme: salivary amylase pepsin bile pancreatic juice Useful nutrients present in food are absorbed in: stomach small intestine large intestine all of these The oxygenated blood is received into heart from lungs through: right atrium left atrium right ventricle left ventricle The loss of water by evaporation from plants is called: translocation transpiration diffusion osmosis Which of the following deficiency may cause anemia? deficiency of calcium deficiency of sugar deficiency of iron deficiency of zinc Seeds of a plant are produced in: stem flower root leaf A bee visits flower for: colour fragrance fruits nectar The specific characteristics are transformed from are generations to the other through: leaves flowers fruits seeds A form part of asexual reproduction is: fertilization pollination spore formation all of these The sunlight energy enters in an ecosystem through: animals sun air plants The organisms that make their own food are called: autotrophs heterotrophs consumers predators Identify the ‘producer’ from the following specie: fungi algae hawk rat A group of elephants living and reproducing in an area is an example of: community habitat population ecosystem The ocean cover the earth: 61% 71% 81% 91% Alum is the name of: aluminium sulphate sodium sulphate aluminium carbonate aluminium phosphate Which of the following species carries negative charge? proton cation anion neutron Identify the reaction responsible for plastic making: hydrogenation polymerization combustion fractional distillation 190 Teacher Resource Pack Guide 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. Science 7 CH4 + 2O2 CO2 + 2H2O CH4 O2 CO2 H2 O Expansion of concrete Total internal reflection occurs: at critical angle after critical angle at the normal in the rare medium A sound wave moves the particles: up and down back and forth in circles with itself During a convection current, which of the following does not happen? hot air sinks hot air rises cold air sinks particles move A metal pot of water is being heated on a stove. Which of the following process is NOT happening? conduction convection radiation evaporation Which of the following is most suitable for making ladles? wool copper wood iron To reverse the flow of heat one must: put the hot body close to the cold body keep both bodies hot keep both bodies cold provide energy to the cold body A vacuum flask prevents: conduction convection radiation all of these Which of the following combinations represents primary colours? red, yellow, blue red, purple, blue red, green, blue red, orange, green An opaque object is coloured because of absorption of all of light reflection of all of light absorption of all components except one reflection of all components except one The principle of a reflecting prism is: reflection dispersion refraction total internal reflection A prism based periscope is better because: it produces a clear, magnified image prisms do not rust like aluminum coated mirrors both of these prisms disperse light Which of the following monitors the leakage current? Earth wire MCB ELCB Fuse Which of the following carries excess charge away from the metal casing of an appliance? live wire neutral wire earth wire fuse Electric current can be used: only in light bulbs only as a magnet only a source of chemical reactions to produce lighting, heating, magnetic effect, and chemical effect Electric current in metals is due to the flow of: protons electrons nuclei both protons and electrons The mirror used at the rear end of a telescope is made: plane convex concave refracting 191 Teacher Resource Pack Guide 37. 38. 39. 40. Science 7 The claim of the big bang is supported by: expansion of the universe cosmic microwave background both expansion and cosmic microwave background evolution of life on Earth Which of the following statements is not correct about a galaxy? it may have different shapes it contains black holes it contains moons light can travel across it in just a year An average-sized star becomes a: red giant nebula both red supergiant Which of the following galaxies contains arms? elliptical irregular spiral none Section – B: Constructed Response Questions Marks: 60 Time: 2 hours 10 minutes Q.1: (a) What are alveoli? (1) (b) Briefly describe the mechanism of breathing. (3) (c) Draw and label the structure of human respiratory system. (2) Q.2: (a) Define circulatory system. (2) (b) Compare the structures and functions of arteries and veins. (4) Q.3: (a) Define an ecosystem. (2) (b) Describe the biotic factors in an ecosystem. (2) (c) Enlist the peculiar features of forest habitat. Q.4: (a) What treatment is used in make to water mineral free? (3) (b) Fill the electrons in 16S, also draw the diagram. Q.5: (a) Explain with examples that physical and chemical changes may occur simultaneously. (3) (b) What are the harmful effects of using hydrocarbons as fuels? (3) Q.6: (a) How is electricity hazardous? (2) (b) Write a detailed note on the differences between conduction, convection and radiation.(4) Q.7: (a) What do voltage and resistance signify? (2) (b) What causes refraction? (2) (c) How does a solid conduct heat? (2) Q.8: (a) How does a swimming pool appear less deep? (2) (b) Explain the step by step process of flow of electric current through a household circuit. (4) Q.9: (a) What causes ringing in telephone sets? (2) (b) Write a detailed note on refraction, its cause and its occurrence in the environment. (4) Q.10: (a) What is the purpose of the kilowatt hour? (2) (b) Explain the working of different safety devices used in household circuits. (4) 192